This is the optional ST Racing Aluminum Rear Shock Set in Gun Metal Gray for the HPI Blitz and E-Firestorm. FEATURES: CNC machined aluminum bodies Preload collars with O-ring installed keeps adjustments in place Lower shock caps keep the shock cartridge straight and flex free during suspension operation and heavy compression INCLUDES: Two each, Bodies, Preload Collars with O-Rings, and Lower Shock Caps REQUIRES: ST Racing HD Upper Shock Caps in Gun Metal Gray, STRC4031 jxs 09/24/12 ir/jxs