Prototype 04 — a carbon-plated trail racing shoe for 50K to 100 miles.

Weight by part at EU 43: upper 42 g, foam 92 g, plate 22 g, carrier 12 g, outsole 50 g; 218 g in all.

218 grams with a carbon plate and 3 mm lugs.

38/30mm of cushion, heel / toe
8mm drop
3mm lugs, ApexTack rubber

218 Grams between you and the mountain.

Prototype 04 from the side: dark knit upper with volt stripes, white foam midsole, black lugged outsole.

Not on sale yet. Prototype 04 is in field testing: pin on a bib and we'll send you a pair to run in. Expected price at launch: $250.

Run the course30 km · 760 m of climbing · 4 checkpoints

Checkpoint 1: kilometre 6, 300 metres climbed.

What 30 km of hills does to you.

A simulated 30 km trail run with 760 m of climbing. Drag the runner along the course and watch the hills go to work: heart rate climbs, each foot stays down longer, steps get shorter, and the plate keeps handing energy back.

Drag or click the chart, or use the arrow keys. Shift jumps 5 km.

High point · 460 m

heart rate · beats a minute: 142
foot on the ground · milliseconds: 182
steps a minute: 182
energy handed back · %: 84

Simulated data. Not a real athlete's file.

Checkpoint 2: kilometre 14, 340 metres climbed.

Slice it open.

Scroll and a cutting plane runs through Prototype 04 from heel to toe. Watch 38 mm of cushion under your heel thin to 30 mm at the toe, the carbon plate fork under the forefoot, and five layers add up to 218 grams.

Prototype 04 seen from behind the heel: dark knit upper, white foam midsole, the edge of the carbon plate and a lugged black outsole.

Keep scrolling. The cut starts at the heel.

The upper · 42 g
The fabric that wraps your foot
Engineered knit in high-strength polymer thread
The foam · 92 g
The soft cushion you land on
Supercritical-foamed PEBA
The plate · 22 g
The stiff spring under your foot
2.2 mm carbon-fibre plate, forked under the forefoot
The carrier · 12 g
The firmer foam the plate rests on
Firm EVA blend, keyed into the plate's fork
The outsole · 50 g
The rubber tread that grips the trail
3.0 mm lugs in ApexTack, a sticky wet-rock rubber

38.0mm between your foot and the ground, here

The five layers add up: 42 plus 92 plus 22 plus 12 plus 50 equals 218 grams.

Cut position, heel to toe

Checkpoint 3: kilometre 22, 760 metres climbed.

Wind at race pace.

Kilometre 22. Your calves have opinions now, and the air is pushing back. A slimmer toe and a lower profile shove less of it out of the way. Pick a pace to see what that's worth.

Prototype 04 from the side, toe pointing into the wind: a low, slim toe and a smooth heel.

Air speed

15km/h25km/h35km/h

Standard trainer · drag 0.44

Prototype 04 · drag 0.31

1.0W

saved per pair at 25 km/h · illustrative

About a watt. You won't feel it. Your splits might.

Illustrative maths: drag power grows with air speed cubed. Not wind-tunnel measurements.

Prototype 04 — a carbon-plated trail racing shoe for 50K to 100 miles.

What 30 km of hills does to you.

Slice it open.

Wind at race pace.

Pin on your bib.