This is the Pro Molded Inner Foam Inserts for 24mm Tires from HPI

FEATURES: Rubber tire inserts.
          Helps increase grip and stability of tires.
          Prevents tires from caving in during high speed & cornering.
          Red / Medium Soft.

INCLUDES: Two rubber inserts

SPECS:    Width:            19mm (13/16")
          Outside Diameter: 60mm (2-3/8")
          Inside Diameter:  46mm (1-13/16")

COMMENTS: This is installed between the tire and wheel so they resist moving
            while the car is cornering.  For really high-grip tracks, use
            a firmer tire insert in the front with a softer insert in the rear.

                                                                   tjt 12/22/99
                                                                          ir/jl