FYI:
The Pagid compound page.
The RS421 is actually OE on:
AMG
Aston Martin
BMW Motorsport
Bugatti
Callaway
Ferrari
GM Performance Division
Lotus
Maserati
McLaren
Multimatic
Pratt & Miller Engineering
Porsche
AG
Porsche Motorsport North America
Riley Technologies
The BIG dog tuners. WOOF.