This is a set of Tamiya JR PRO Low Friction Roller Set. The Low Friction Roller Set is lightweight, cost effective, offers enhanced performance, and can be used with all Mini 4WDs. Polyacetal resin reduces, providing even smoother rotation. As shown in the image above, this roller set includes high-strength 19mm and 16mm rollers, with the 19mm rollers being 43% lighter than aluminum rollers. Also included are brass made roller receivers made from brass, screws, nuts, and washers.