Prototype 04 — Carbon-plated trail racing shoe
Prototype 04 is a trail racing shoe built for 50K and longer. A carbon plate under the forefoot gives back 84% of the energy you put into every stride, so the last hour of a race feels closer to the first. Explore the concept through interactive, simulated test data below.
- Weight
- 218 g
- Stack height
- 38 / 30 mm
- Built for
- 50K – 100 mi
What 30 km does to your stride.
Explore a simulated 30 km trail run. Drag across the hills to move through it and watch what the climbs do to a runner: heart rate climbs, each foot stays on the ground longer, steps get shorter — and the plate keeps handing energy back.
Scroll to play the run — drag, or use the arrow keys, to take the controls.
- Heart rate
- 142 bpm
- Foot on ground
- 182 ms
- Step rate
- 182 /min
- Energy returned
- 84 %
Three layers, peeled back.
A running shoe is really just three parts stacked together: the fabric that wraps your foot, the cushioned slab underneath it, and the rubber that touches the trail. Keep scrolling to take Prototype 04 apart one part at a time.
All three together 218 g per shoe
The fabric that wraps your foot
This is the part your foot actually sits inside, and it is one single stretched sheet of fabric rather than stacked, stitched panels — so there is no seam left to rub a blister over 50 km. The sheet is woven from 0.4 mm Vectran filament held under tension, and heat-welded overlays lock your midfoot down when the trail tilts sideways.
Tear strength: 38 N (ASTM D2261)
- Material
- Vapor-permeable monomesh, welded overlays
- Spec
- 0.4 mm filament / 78% open-air weave
- Weight
- 42 g
- Layer
- 01 / 03
Less drag. Free speed.
Every shoe shoves air out of the way, and that costs you energy. A narrower toe box and a lower profile shove less. This simulated wind-tunnel comparison shows how the estimated power changes at different speeds.
Estimated power saved from drag reduction alone, holding pace and position constant.
12Westimated saving
Two fields · about thirty seconds
Get on the start line.
Prototype 04 field allocation is limited to athletes racing this season. Tell us your distance and size and we hold a pair for testing.
- Race distance
- 50K
- Ground
- Singletrack, loose rock
- Size
- EU 43
- Stack height
- 38 / 30 mm
- Weight per shoe
- 218 g
Deeper lugs bite soft ground on long mountain days; shallower lugs roll faster on hardpack.