Leading with the guarantee, not the shoe

Every runner's ad talks about foam and drop. We led with Fieldday's 100-mile guarantee instead, and cost per purchase fell by almost half.

Cost per purchase

$41 → $25

Over 5 weeks

Past results, not a promise.

Client

Fieldday Run

Running shoes

Channels

TikTok, Meta

Monthly spend

$48k

The brief

Fieldday makes one trail-and-road shoe at $138 and offers something no big brand does: run 100 miles in them, and if you don't love them, send them back worn. Their ads didn't mention it. They looked like every running ad on TikTok: slow-motion strides, foam close-ups, numbers about stack height. Cost per purchase was $41 and climbing, on $48k a month.

Marcus, their head of growth, suspected the guarantee was the real product. He'd never had the budget to test it properly.

What we made

We wrote eight ads around one idea: the risk is on us. Two opened on the guarantee in the first second ("Wear them 100 miles. Or send them back."), two buried it at the end, and four tested different proofs (a return label in a shoebox, a runner's Strava screenshot at mile 97, a founder explaining why). Same shoe footage underneath, so the only thing changing was the opening.

Both guarantee-first ads beat everything else inside four days. The winner opens on a runner on a dirt trail and the line, in plain white text, before the shoe is even in frame. It cut cost per purchase from $41 to $25 and still holds after five weeks, now on Meta as well as TikTok.

What didn’t work

We expected weight to matter to runners, so we made a static ad of the shoe on a kitchen scale: "Lighter than your last pair." It had the lowest hook rate of the batch and we switched it off on day three. Returns did go up a little, from 4% to 6%, which Fieldday had planned for; profit per order still rose.