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Description
e fatbike fully ELECTRIC FAT TIRE E-BIKEIntroducing the all new Keystone Electric Fat Tire Bike. Since 2013, Borealis has specialized in lightweight, high end fat bikes. The Keystone is our first ever Class I electric bike. The frame geometry is optimized for riding just about anything with clearance for up to 5 wide tires. Paired with the most technically advanced components in the industry, the Keystone sets the standard for premium quality Electric fat bikes. HIGHLIGHTS Color: Gunmetal
Introducing the all-new Keystone Electric Fat Tire Bike. Since 2013, Borealis has specialized in lightweight, high end fat bikes. The Keystone is our first ever Class I electric bike. The frame geometry is optimized for riding just about anything with clearance for up to 5” wide tires. Paired with the most technically advanced components in the industry, the Keystone sets the standard for premium quality Electric fat bikes.
HIGHLIGHTS
- Color: Gunmetal Grey with Cobalt Blue Graphics
- Weight: 56 lbs. as shown.
- Standard features include Shimano EP8 Drive Unit, Shimano 630Wh Battery, SRAM G2 RS brakes, Mastodon Pro EXT 120mm suspension fork, carbon handlebars, dropper seat post, durable Sun Ringle Mulefüt rims and your choice of tires.
- Frame geometry provides responsive handling, offering maximum control for varying conditions in snow or sand.
- Tire clearance up to 26x5” and 27.5x4.5”.
- Lightweight, 6000 series aluminum frame comes with internally routed cables, 1-2 bottle cage mounts and lizard skin protection.
- Keystone Frames are backed by our LIMITED LIFETIME WARRANTY.
ASSEMBLY
Some assembly required upon receipt. Your bike will be completely assembled and tuned by Borealis, then partially disassembled for shipment. The remaining assembly will require installation of the rear derailleur, chain, fork, seat post, wheels, and handlebars. A kit will be included with your order that has all the necessary tools assemble your bike, including a multi-tool, torque wrench, and shock pump. If you are not familiar with this level of assembly, we recommend having your local bike shop complete the assembly.
Stay tuned for our step-by-step assembly video.
WHEELS AND TIRES
- All bikes come standard with tubes.
- If you order rim tape with your Mulefut rims, we will tape the rims and install the tires with tubes.
- Tubes must be removed and tubeless valves installed for tubeless set up. We recommended to have this completed by a professional bicycle mechanic.
SIZE CHART
BUILD SPECS
| Frame | Borealis Keystone Aluminum 15", 17", 19", 21" |
| Drive Unit | Shimano DU-EP800 |
| Battery | Shimano BT-E8036 (630Wh) |
| Display | Shimano SC-EM800 |
| Assist Switch | Shimano SW-EM800L |
| Speed Sensor | Shimano EWSS300L540A |
| Fork | Manitou Mastodon PRO EXT 120mm, 51mm offset |
| Headset | FSA w/ Star Nut |
| Stem | Borealis 50mm |
| Handlebar | Borealis Carbon |
| Grips | Ergon GP1 |
| Saddle | WTB Volt Medium Steel |
| Seat Collar | Borealis Bolt-On |
| Seatpost | KS Lev Integra 125mm (SM, MD) / 150mm (LG, XL) |
| Brakes | SRAM G2 RS |
| Rotors | SRAM HS2 200mm front / 180mm rear |
| Shifter | SRAM AXS Pod Contoller Right Bridge w/ MMX Clamp for GX Eagle Transmission |
| Derailleur | SRAM GX Eagle Transmission Derailleur |
| Cassette | SRAM GX Eagle Transmission Cassette 10-52T |
| Chain | SRAM GX Eagle Transmission Flattop Chain |
| Crank Arms | Samox 170mm |
| Chainring Mount | Samox 104 BCD for 75mm chainline |
| Chainring | SRAM Eagle Transmission E-Bike MTB Chainring 104 BCD 36T Steel |
| Rims | Your choice of SunRingle Mulefüt SL - 26x80, 27.5x80, or 27.5x65 |
| Spokes | Straight Gauge 2.0 Black |
| Hubs | Borealis Gen 4 15x150 / 12x197 |
| Tires | Your choice. All tire options are listed online. |
| Included | Shimano ECE80042 Battery Charger, AXS Power Pack, Kickstand, UDH Hanger, Key for battery release, Borealis Rear Thru Axle, Remote Battery Charging Adapter |
| Weight | Size Medium w/ Mulefut 27.5x80 & Terrene Yippee Ki Yay 4.3" Tires: 56 lbs. |
FRAME SPECS
| Wheel / Tire Size | 26 x 3.8–5.0" on up to a 100mm rim / 27.5 x 2.8-4.5 on up to a 82mm rim / 29 x 2.25–3.0 |
| Susp Fork Travel | 120mm |
| Fork Offset | 51mm |
| Headset-Upper | IS41 |
| Headset-Lower | IS52 |
| Seatpost | ø31.6mm |
| Seat Collar | ø34.9mm |
| Dropper Compatible | Internal - 125mm for SM & MD / 150mm for LG & XL |
| Front Derailleur Type | Not Compatible |
| Bottom Bracket | Shimano EP8 |
| Crankset (Max Ring) | Chainline 75mm / 1x (38t) |
| Rear Brake (Rotor) | 74mm post (160–180mm) |
| Rear Spacing | 197 x 12mm thru-axle |
| Rear Axle | ø12 x 222L, TP= 1.0, TL = 16 |
| Derailleur Hanger | SRAM UDH |
| Bottle Mount | Small & Medium: 1 (downtube) / Large & XL: 2 (downtube & seatube) |
| Rear Rack Reccomendation | Old Man Mountain Divide Fat |
| Rear Rack Mounts, Upper | Yes |
| Axle to Crown | 531mm |
| Steerer Tube Size | 28.6mm |
| Steerer Style | Tapered |
| Crown Seat Diameter | 40mm |
GEOMETRY CHART
| Small 15" | Medium 17" | Large 19" | X-Large 21" | |
| Effective Top Tube | 630 | 645 | 660 | 665 |
| Seat Tube Center to Top | 381 | 432 | 482 | 533 |
| Head Tube Length | 160 | 160 | 175 | 190 |
| Head Tube Angle | 69° | 69° | 69° | 69° |
| Seat Tube Angle | 73° | 73° | 73° | 73° |
| Chainstay Length | 480 | 480 | 480 | 480 |
| BB Drop | 60 | 60 | 60 | 60 |
| Reach | 420 | 435 | 445 | 446 |
| Stack | 688 | 688 | 702 | 716 |
| Standover Height | varies based on wheel and tire size | |||
| Wheelbase | 1187 | 1207 | 1223 | 1229 |
| Fork Offset | 51 | 51 | 51 | 51 |
FAQ:
| Can I use the Keystone in cold temperatures? | It is okay to use your Keystone in the operating temperature range, suggest by Shimano: -10 - 50°C |
| How do I remove the battery? | Each Keystone will come with a set of keys. Make sure to save your spare key and safe location. Insert the key fully into the lock cylinder on the non drive side of the downtube until it stops. Rotate the key clockwise until the battery drops from the downtube providing access to the latch release mechanism. Use your index finger to gently depress the spring which will fully release the battery. Use caution to support the battery when removing it so it does not fall to the ground. |
| How can I file a warranty claim for the drive unit and other electronic components? | Contact an authorized Shimano STEPS dealer. |
| Can I change my motor/power settings? | Yes, you can customize your motor settings via the app as well as update the firmware. You'll need to download the Shimano E-tube mobile app. |
| Can I change the max speed? | No. Depending on where you've purchased your Keystone it will either have a max assist speed of 20mph or 25km/h. This setting cannot be modified by the user or a dealer. |
| Can I purchase an extra battery? | Yes, you can purchase a spare battery kit with a spare downtube cover directly from Borealis. Spare battery kits may not be available in all markets. You can also purchase a spare battery from Shimano, but it will not include a battery cover. |
| Can I ride the Keystone without the battery? | No. This will void your warranty with Shimano and cause damage to the motor system. |
| Do I need to update the firmware / software? | Firmware can be updated via the Shimano E-tube mobile app. |
| How do I use walk mode? | Hold the upper button (down assistance level) for 1 second until the display turns blue and displays WALK mode. Press and hold the same button to power the rear wheel. |
| How long does it take to charge the Shimano 630Wh Battery? | With the included EC-E8004 charger, the battery can fully charge in 6 hours. |
| How long will my battery last? | The remaining battery capacity is affected by temperature and cycle count. Generally, it decreases approximately 5% a year. This means roughly 95% capacity remains after 1 year, and 90% after 2 years. |
| How should I store my bike and or battery? | Charge your battery to approximately 70% before storing for long periods of time. Store in a cool, indoor location with a stable temperature between approximately 10 - 20 C / 50 - 70 F. No direct exposure to sunlight or rain. |
| Are the electronic components waterproof? | Yes, the STEPS system is waterproof as long as all components of the system, including the battery and battery cover, are installed correctly. We recommend not using a high-pressure washer to clean your Repeater, but riding in the rain and regular cleaning are okay. |
| My bike won't turn on, what do I do? | First, make sure all cables are plugged in, if they are then try removing and reinstalling the battery. If it still won't turn on try charging your bike for a few hours. If your bike is too hot or too cold, it might not turn on. If your bike still does not turn on, contact a Transition or Shimano dealer for support. |
| Should I only charge my battery when it's completely drained? | No, simply charge the battery any time you need it, frequent charges actually help battery longevity. Avoid letting the battery discharge completely. Charge to 70% before storing for long periods. |
| What are the different error codes and what do they mean? | Whenever you encounter an error code, first cycle the power off and then back on. If the code persists, remove the battery and then reinstall, which will hard reset the system. If neither of these steps resolves the issue, please reference the Shimano error code list. If you cannot resolve your error code via your Etube mobile app please visit your nearest Shimano STEPS dealer or contact Shimano STEPS customer support. |
| What is the range and how can I maximize it? | There are many factors that affect battery range, such as, how much effort the rider is providing, the gradient of terrain, ambient temperature, and rider weight. The best way to maximize your range it to spend more time in Eco and Trail modes, and minimize the amount of time spent in Boost mode. |
| What is the widest tire the Keystone can fit? | 26x5.0" or 27.5x4.5" |
| What kind of maintenance is needed on the drive unit and how often? | The drive unit is sealed and cannot be serviced. If there are any issues with the drive unit, it will need to be removed and sent back to Shimano for service or replacement. The drive unit along with the battery is designed to last over 1000 charge cycles. Assuming you're getting 30 miles (48Km) per charge, the drive unit should last 30,000 miles, or much longer than pretty much any other part on your bike. |
| Why does my bike stop giving assistance over a certain speed? | Depending on where you've purchased your Keystone it will either have a max assist speed of 20mph or 25km/h. This setting cannot be modified by the user or a dealer. |
| Will environmental temperature affect battery life? | The battery life will be shorter during cold temperatures, this is not a sign of a problem. |
| Will my bike be delivered with a charged battery? | Your Keystone was shipped in a "sleep" mode with the battery at approximately 30% charge. It is recommended to fully charge your battery before the first ride. |
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- Standard Shipping : 3-10 business days
- If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy
4.0 ★★★★★
Based on 29 reviews
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Product Reviews
★★★★★ 5
My number one choice for dry mouth. Really works and worth it.
Flavor Name: Slightly Sweet, Size: 100 Count (Pack of 1)
These do work for very dry mouth. My dentist recommended these because l am on a medication that causes dry mouth. I had no idea it could be this uncomfortable ! It gets to the point I cannot spit after brushing my teeth, can’t make the kiss sound to call my dog, even my voice has been affected. It’s the worst.
Sometimes though one tab isn’t enough. I use 3 at once at night. One on each side of mouth between my teeth and cheek, sticking them to my cheek and one on the roof of my mouth. If you have trouble with them sticking to your cheek, definitely try the roof of your mouth.
The taste is extremely mild. It’s hard to describe but the flavor but it’s not unpleasant in any way. I rather like it. You get more of a very slight gel consistency when they melt which is what you want.
They last in my mouth for hours. I haven’t timed it but it’s half a night’s sleep some nights if I’m asleep. During the day they don’t last as long but still a long time.
I’ve been trying different products for dry mouth and I do like to mix it up but this is my go to for serious dry symptoms and nighttime. I really like the sticking feature they have. Will continue to buy.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on March 23, 2026
★★★★★ 5
Good for dry mouth
Flavor Name: Slightly Sweet, Size: 100 Count (Pack of 1)
These are one of the few things that help with the pain of my Sjogren's dry mouth. They stick securely and safely. They have a mild minty taste with no menthol. They dissolve without grittiness. I highly recommend them.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 23, 2026
★★★★★ 4
Works great, not always comfy but I do recommend
Flavor Name: Slightly Sweet, Size: 100 Count (Pack of 1), Flavor Name: Slightly Sweet, Size: 100 Count (Pack of 1)
I am a senior who raised a family, had a career and held down a household. Apparently, however, I’m not competent enough to use a mint 🤷♀️🤣 The first one I tried to “install” ended up in a mess in my lap. After putting on clean pjs I decided to try again, my hubby glanced over and asked why I was trying to stick my fist in my mouth and when I started laughing the mint shot halfway across the room. I am nothing if not persistent, so decided to practice with a couple. I put one in my mouth and attempted to position it with my tongue as the instructions suggest, within 2 seconds it firmly attached to the roof of my mouth. I finally managed to get two stuck onto my gums (using my finger) and they worked perfectly! Of course when I woke up there was a small tan drool spot on my clean pillowcase. I assume it’s from the side of the mint that attaches, which is a tannish brown color. Now I use one per night, they can be really hard to use sometimes but are extremely effective. They have a slightly sweet, very pleasant taste. I use multiple dry mouth products as I have COPD & use oxygen 24/7. I am prescribed 2 inhalers and a nebulizer, all of which cause awful dry mouth - to the point of feeling like my lips are stuck to my teeth some mornings. These are the ONLY things that have made that seem like less of an issue. I sleep an average of 5 hours per night and the mint has already dissolved by then, but my mouth still feels moisturized. I don’t notice any weird taste when I drink a glass of water upon waking, just a pleasant non-taste. I do recommend, just be patient! Photo is front and back next to a Tylenol caplet
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on March 10, 2026
★★★★★ 5
Great product
Flavor Name: Slightly Sweet, Size: 100 Count (Pack of 1)
These are so helpful for me. My dentist in Chicago recommended them about 7 years ago because I have severe dry mouth. Typically I'll use 3 to get me through the night. I'll put another in my mouth after taking a sip of water if needed. These have (I believe) prevented me from having any cavities since I started using Xylimelts. The active ingredient prevents bacteria from attacking my teeth. My dentist has been pretty impressed with the outcome. There are multiple flavors, I like the mild mint and the unflavored ones. They are a little expensive, but well worth the price. Especially with no cavities and being more comfortable at night. I love the fact that they stay where you place them too.
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Reviewed in the United States on February 26, 2026
★★★★★ 5
Dry mouth relief!
Flavor Name: Slightly Sweet, Size: 230 Count (Pack of 1)
My go to dry mouth relief. Tastes good and actually works. I’ve tried all kinds of products but this is my favorite.keep a bottle in my nightstand and I keep some in a small pill jar for my purse.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on April 25, 2026
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