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Description
trek 4100 mountainbike Trek Powerfly FS 4 Gen 2 – Cahaba CyclesPowerfly FS 4 is a full suspension electric mountain bike built to tackle rugged trail adventures. The plush suspension setup soaks up rough terrain, and the powerful Bosch electric drive system boosts your capacity to crush climbs and mile after mile of singletrack. For e MTB, full suspension is a game changer: it soaks up rugged terrain so you can ride the Bosch pedal assist system to its full potential Treks Removable Integrated Battery (RIB)
Powerfly FS 4 is a full suspension electric mountain bike built to tackle rugged trail adventures. The plush suspension setup soaks up rough terrain, and the powerful Bosch electric drive system boosts your capacity to crush climbs and mile after mile of singletrack.- For e-MTB, full suspension is a game-changer: it soaks up rugged terrain so you can ride the Bosch pedal-assist system to its full potential
- Treks Removable Integrated Battery (RIB) system looks great and is super user-friendly: it fully hides the battery in the frame for protection, makes it easy to remove the battery without tools, and lets you mount a water bottle cage—even on full suspension e-MTBs
- The dropper post lets you lower your saddle on the fly so its out of the way on descents
- The Purion controller has Walk Assist and an intelligent eMTB mode that automatically delivers the right amount of power based on your terrain
- Powerfly FS frames feature a curved top tube that makes standing over the bike easier. Plus, Smart Wheel Sizing means youll get the fastest wheel that fits—29˝ wheels on larger frames, 27.5˝ wheels on smaller frames
Bosch Performance Line CX motor
Bosch Performance Line CX sets the standard for eMTB performance with up to 85Nm of torque and an intelligent eMTB mode with Extended Boost that automatically adjusts the amount of assist based on the terrain.
Custom eMTB Lite mode
Trek eMTBs feature a custom eMTB Lite mode in place of Tour mode. It gives you more natural-feeling power delivery and longer battery life.
Removable Integrated Battery
RIB is a one-piece battery and cover with a built-in handle that can easily be removed and re-installed in the frame with no tools and no hassle. It’s the most convenient way to remove your battery for transport, security, or just easier charging.
What is the range?
To see how far you can ride your electric mountain bike on a single charge, check out Bosch’s range calculator. We’ve auto-filled the variables for this bike model and the average rider, but you can make adjustments to get your most accurate estimate.
Compliant with leading safety regulations
The e-systems on Trek and Electra e-bikes are third-party tested to meet the latest e-bike safety regulations, including the stringent UL 2849 certification — so all you have to worry about is where your e-bike will take you next.
| Frame | Alpha Platinum Aluminum, Removable Integrated Battery (RIB), tapered head tube, internal routing, Motor Armor, magnesium rocker link, rack and fender mount, ABP, Boost148, 100mm travel |
| Fork | SR Suntour XCR 34, air spring, LO R damper, hydraulic lockout, tapered steerer, 41mm offset, oversized crown for eMTB, Boost110, 15mm bolt-on thru axle, 100mm travel |
| Shock | SR Suntour Edge R, 190mm x 45mm |
| Tire | Bontrager XR3 Comp, wire bead, 30tpi, 27.5x2.35 |
| Hub Front | Bontrager sealed bearing, alloy axle, 6-bolt, Boost110, 15mm thru axle |
| Hub Rear | Bontrager Approved DC-3248, sealed bearing, alloy axle, 6-bolt, Shimano 8/9/10 freehub, Boost148, 12mm thru axle |
| Rim | Alex MD35, tubeless compatible, 32-hole, 35mm width, Presta valve |
| Rim Strip | Bontrager TLR |
| Spokes | 14g stainless steel, black |
| Skewer Rear | Bontrager Switch thru axle, removable lever |
| Shifter | Shimano Deore M4100, 10 speed |
| Rear Derailleur | Shimano Deore M5120, long cage |
| Crank | FSA Bosch CK-220, 36T ring, 165mm length |
| Cassette | Shimano Deore M4100, 11-46, 10 speed |
| Chain | KMC X10, 10 speed |
| Chainring | FSA, 36T, steel |
| Brake Rotor | Tektro, 6-bolt, 203mm |
| Pedal | VP-536 nylon platform |
| Saddle | Bontrager Arvada, steel rails, 138mm width |
| Seatpost | TranzX JD-YSP18, 100mm travel, internal routing, 31.6mm, 361mm length |
| Seat Collar | Bolt-on, 36.4mm |
| Handlebar | Bontrager alloy, 31.8mm, 15mm rise, 720mm width |
| Stem | Bontrager Comp, 31.8mm, Blendr compatible, 7 degree, 60mm length |
| Headset | FSA IS-2 |
| Grips | Bontrager XR Trail Comp, nylon lock-on |
| Fender | Trek Powerfly 29 custom fender |
| Battery | Bosch PowerTube 500Wh |
| Motor | Bosch Performance CX, magnesium motor body, 250 watt, 85 Nm, 20mph or 32km/h max assist |
| Charger | Bosch compact 2A, 100-240V |
Geometry Chart
| B B Drop | 2.4 |
| B B Height | 33.2 |
| Chainstay Length | 46.8 |
| Eff Seat Tube Angle | 76.0° |
| Eff Top Tube | 55.4 |
| Frame Reach | 40.5 |
| Frame Size Letter | XS |
| Frame Size Number | 14.5 |
| Frame Stack | 59.9 |
| Head Angle | 66.5° |
| Head Tube Length | 14 |
| Offset | 4.4 |
| Seat Tube | 36.8 |
| Seat Tube Angle | 68.3° |
| Standover | 69.1 |
| Trail | 10.7 |
| Wheelbase | 117 |
| Wheel Size | 27.5" |
| B B Drop | 2.4 |
| B B Height | 33.2 |
| Chainstay Length | 46.8 |
| Eff Seat Tube Angle | 76.0° |
| Eff Top Tube | 56.4 |
| Frame Reach | 41.5 |
| Frame Size Letter | S |
| Frame Size Number | 15.5 |
| Frame Stack | 59.9 |
| Head Angle | 66.5° |
| Head Tube Length | 14 |
| Offset | 4.4 |
| Seat Tube | 39.5 |
| Seat Tube Angle | 68.3° |
| Standover | 69.1 |
| Trail | 10.7 |
| Wheelbase | 118 |
| Wheel Size | 27.5" |
| B B Drop | 3.9 |
| B B Height | 33.5 |
| Chainstay Length | 47 |
| Eff Seat Tube Angle | 76.0° |
| Eff Top Tube | 58.9 |
| Frame Reach | 43 |
| Frame Size Letter | M |
| Frame Size Number | 17.5 |
| Frame Stack | 63.7 |
| Head Angle | 66.5° |
| Head Tube Length | 13 |
| Offset | 4.4 |
| Seat Tube | 42 |
| Seat Tube Angle | 67.5° |
| Standover | 71.2 |
| Trail | 11.4 |
| Wheelbase | 120.6 |
| Wheel Size | 29" |
| B B Drop | 3.9 |
| B B Height | 33.5 |
| Chainstay Length | 47 |
| Eff Seat Tube Angle | 76.0° |
| Eff Top Tube | 62.1 |
| Frame Reach | 46 |
| Frame Size Letter | L |
| Frame Size Number | 19.5 |
| Frame Stack | 64.6 |
| Head Angle | 66.5° |
| Head Tube Length | 14 |
| Offset | 4.4 |
| Seat Tube | 45 |
| Seat Tube Angle | 67.5° |
| Standover | 71.6 |
| Trail | 11.4 |
| Wheelbase | 124 |
| Wheel Size | 29" |
| B B Drop | 3.9 |
| B B Height | 33.5 |
| Chainstay Length | 47 |
| Eff Seat Tube Angle | 76.0° |
| Eff Top Tube | 64.6 |
| Frame Reach | 48.5 |
| Frame Size Letter | XL |
| Frame Size Number | 21.5 |
| Frame Stack | 64.6 |
| Head Angle | 66.5° |
| Head Tube Length | 14 |
| Offset | 4.4 |
| Seat Tube | 50 |
| Seat Tube Angle | 67.5° |
| Standover | 71.3 |
| Trail | 11.4 |
| Wheelbase | 126.5 |
| Wheel Size | 29" |
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
4.5 ★★★★★
Based on 1741 reviews
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Product Reviews
★★★★★ 5
Great pillow, but the cooling effect depends on the cover
Color: Blue-ice Plus, Size: King(Pack of 2)
I really like this pillow overall. It’s comfortable, supportive, and feels well made. When you use it without a pillowcase, it definitely feels cool to the touch and does what it claims in terms of that initial cooling sensation.
However, once you put a pillowcase on it, you can’t really feel the cooling effect anymore. I’ve tried multiple different pillowcases made from different materials, and none of them really let that cool feeling come through.
That said, I still love the pillow itself. It’s comfortable and supportive enough that I’m keeping it. Just keep in mind that the cooling feature works best without a cover, which isn’t ideal for everyone.
Overall, a good pillow — just manage expectations about the cooling effect once it’s covered.
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Reviewed in the United States on February 17, 2026
★★★★★ 5
Cooling and holds shape.
Color: Blue-ice Plus, Size: Queen(Pack of 2), Color: Blue-ice Plus, Size: Queen(Pack of 2)
Very nice pillow for the price is also holding up well and holding shape very cool and comfortable to the touch. Best pillow I found in a long time.
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Reviewed in the United States on April 28, 2026
★★★★★ 5
Best Pillow Ever
Color: Blue-ice Plus, Size: Queen(Pack of 2)
Best pillow ever. Although it still gets "hot", it does take longer to get "hot". I love this pillow. I was buying a new pillow almost every 3 months. Other pillows would either remain rock hard or go flat. I was concerned at first when reading the description as I though the memory foam would be big pieces. They are soft fluffy pieces. I had to remove almost half of the foam to get the pillow to what works for me. I have not had to put any filler back in. Maybe in a couple of more months I may have to put a bit more in, but it is holding it's shape and not going flat. I do fluff it every night. This helps. I am a stomach sleeper. I have bought the expensive purple pillow and hated it so much I gave it to my daughter. This QUTOOL Pillow is the best! I bought a 2 pack. Have not used the other pillow yet, but I feel I may actually go years for once without having to buy a pillow as I have the 2nd one set aside if the first one gets to a point in need replacement. I have bought Dollar Store pillows. I have bought $300 pillows. None of them even come close to this pillow and the way you can adjust this pillow for you. The pillows came in a white mesh like bag. I keep all the unused "stuffing" in this bag. I have it hanging in my closet and I just fluff the bag once a month to keep the filling fresh so it is ready if and when I need it. Coming from someone who has trouble staying asleep, neck issues, a stomach sleeper who hate those flat pillows manufacturers think stomach sleepers like but actually hate, buy this pillow. Just buy it. Best Pillow for a picky person like me. Buy 2 or more so if you have to stay at a hotel, you can take your own pillow.
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Reviewed in the United States on June 15, 2025
★★★★★ 4
Slippery Pillow
Color: Blue-ice Plus, Size: Queen(Pack of 2)
Nice and cooling but it’s so slick my pillow sheet doesn’t want to stay on.
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Reviewed in the United States on May 14, 2026
★★★★★ 5
Foam Mattress NEEDs Foam Pillows
Color: Blue-ice Plus, Size: King(Pack of 2), Color: Blue-ice Plus, Size: King(Pack of 2)
10 stars!! Quality foam, structure & price. Best bang for my buck.
HRV, readiness & total sleep score metrics increased drastically this week. See screenshot :)
Support:
Molds and cushions every crevice under my neck and above shoulders. So comfy
Size:
Adjustable loft but king length is perfect to hug and rest your head. Love love love. The 1st 2 nights were uncomfortable with pillow as is, first night I was up at 3am half asleep pulling foam out but wasn't enough. The second night at 2am I pulled out more stuffing. I was getting frustrated.. my Oura ring showed both nights I was awake every hour. Not good. Before the 3rd night I pulled enough to fill the bag the 2 pillows arrived in. Boom -8hrs sleep and for the first time ii years I achieved 17% Deep sleep. Huge.
Weight:
Perfect weight with adjustment. Squishy and molds to b the contour of my neck and shoulders
Softness:
Like the baby bear.. just right.
Comfort:
Very comfortable after removing 30% foam in both pillows. I actually now have enough to make a 3rd pillow, replace old foam, or adjust OGs, Still to early to measure.
If you have a foam mattress that contours your body but not your head you'll end up with neck and/or back pain from head being elevated- not sinking/molding the body into a foam mattress.
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Reviewed in the United States on July 1, 2025