Matter Juice F1 Yellow:
The most competitive wheel available. Features Hollow Core and EMT Technology, High rebound, and incredible performance. Best used on all asphalt or track surfaces.
F1 is the hardest, very fast and best for smooth surfaces.
Rated by Footprint and not just Durometer(hardness).
Footprint is more important than wheel hardness alone. Footprint is the compression size. In other words the amount of wheel making contact to the surface. This changes with someone’s weight, speed, temperature and becomes even more important when you are on the side of the wheel in the turns or doing the double push.
The smaller the footprint, the harder the wheel.
(Softest) F4 — F3 — F2 — F1 — F0 (Hardest)