These back-up rings, made from urethane or nylon, are commonly used as spacers for u-seals.

SEAL INFORMATION
MATERIAL URETHANE, 70 SHORE D
TEMPERATURE RANGE -40° to +250° F
SPEED 3 FT/SEC
PART NUMBER (Prefix) (CS) – (ID) – (Width)
N = Nylon
S = Split
P = Hard Hytrel