This is the replacement Suspension Arm Set and drive washers for the HPI RS4 MT 2 (HPIC1401). FEATURES: Black nylon construction INCLUDES: Two nylon suspension arms (will work on front or rear of the truck) Two nylon drive washers (hex shaped washers that fit in the wheel and and key into the axle) REQUIRES: Assembly onto model following the manual that came with the original truck. SPECS: Length: 4" (101mm) Width: 1.5" (57mm) tapering down to 1" (25.4mm)