Track Form

The best Track Form part for a 2015-2020 WRX or STI in this collection is its Gurney flap, listed for the 15-20 WRX/STI: a small trailing-edge lip for the rear spoiler that adds downforce without replacing the whole wing. It is an aero finishing piece for owners who already run the factory-style spoiler and want more rear grip at speed.

A Gurney flap is a short vertical lip fitted to the trailing edge of a wing or spoiler. It changes how air separates off the back of the blade, increasing the downforce the spoiler makes, at the cost of a little drag — which is why flaps are a track and fast-road tuning tool rather than a styling part. Because this one is listed for a specific spoiler application, fitment is the whole decision: it is made for the 15-20 WRX/STI fitment named in the product title, so check your year and model and your spoiler style before ordering.

Compare it with the wider Aero range and the Exterior Trim shelf, and read our explainer on the purpose of rear wings and spoilers.

Brands to know

Track Form is represented here by this single, application-specific product: a Gurney flap listed by model years, 15-20 WRX/STI, rather than a universal strip cut to length. That specificity is the brand's pitch in this catalog — a small aero part shaped for one spoiler, bought to finish a rear aero setup rather than start one.

APR Performance is the full-wing end of the same decision, known for the GTC-300 wing and track-focused aero for WRX and STI builds. Owners cross-shop a flap against a full wing when deciding how much downforce hardware their car actually needs.

Rexpeed covers the carbon fiber aero and trim side for Subaru and other Japanese platforms, with lips, spoilers, and dress-up pieces listed by model. Its shelf is where a Gurney flap buyer usually also looks for matching carbon exterior pieces.

Seibon is the established carbon fiber body brand in this group, known for hoods, trunks, and aero panels that cut weight while changing the car's look. Verus Engineering takes the functional aero route, with splitters, diffusers, and wing hardware developed for track use on the same WRX and STI platforms.

FAQ

Will this Gurney flap fit my WRX or STI?

It is listed for the 15-20 WRX/STI. Other years use different spoilers, and not every 15-20 car carries the same spoiler style, so check your year and model and spoiler type before ordering.

What does a Gurney flap actually do?

It increases the downforce made by the spoiler it is fitted to by changing airflow off the trailing edge. The gain comes with some added drag, so it suits drivers who use the car at speed rather than pure styling builds.

How hard is it to install?

Flaps are a light exterior job, typically fitted to the spoiler's trailing edge with fasteners or adhesive. Surface preparation and alignment decide how clean the result looks, so test-fit first.

Should I buy a flap or a full wing?

A flap builds on the spoiler you already have and is the smaller commitment. A full wing replaces the aero entirely and suits dedicated track builds; most street and mixed-use cars start with the flap.