This is the Short Course Inner Foam Set for the HPI Blitz (HPID10**). Medium Inner and Outer foam Smaller Foam Controls Forward Bite and Response On Jumps and Landings Larger Foam Controls Side Bite on Corners and Overall Straight Line Bite Two Larger Foams Two Smaller Foams Installation onto Vehicle Tire Glue (DTXR2000) or (DTXR2002) Large: Outer Diameter: 3.88" (98.64mm) Inner Diameter: 2.75" (69.75mm) Width: 1.52" (38.5mm) Thickness: 0.60" (15.3mm) Small: Outer Diameter: 2.62" (66.5mm) Inner Diameter: 1.94" (49.25mm) Thickness: .38" (9.6mm) lmm 11.13.09 ir/jxs &