APS™ (Animated Polymer Systems) compound Lively and responsive, high-performance urethane with just the right amount of rebound. Very linear in response so you can control the bushing instead of the other way around.
Hints in choosing Hardness: They feel softer compared with similar durometer of other brands (e.g. Bloodorange, Venom, etc.) , so normally people pick greater duros than those they used to ride on.