STEP PIN PRO-87 M3 2.15 REAR BUGGY (2) M3 compound is ULTRA Soft. Step pins are a tread pattern consisting of lugs(pins or studs) of two different diameters. The part of each lug which actually touches the track first(the part that is furthest from the carcass of the tire itself) is a smaller diameter, while the part of the stud that actually emerges from the carcass of the tire is larger diameter. These are excellent all around tires. Work in both loose and hard pack conditions due to their two diameter lug design. In wet conditions, step pins are the only choice, because the wet mud will bcome clogged in regular tire, whereas with a step pin, pin it will only clog the larger diameter lugs, leaving the portion of the lug closer to the track free of mud, and still able to get traction. INCLUDED: Two Step Pin 2.2" rear buggy tires(will fit wheels from 2.15 to 2.2") AND Two Foam Inserts SPECS: Inside Diameter: 2.2" Width: 1.86"