This is the Acer Racing Ceramic Nitride Pro Series Bearing Kit for the Traxxas E-Revo. FEATURES: Assembled with diamond polished super lightweight Ceramic Nitride Balls which do not deform under load and also insure low friction and low heat buildup Over 33% less bearing friction compared to conventional bearings Exclusive no contact seals for the lowest friction and best dirt resistance Lightly oiled with Acer"s SIN synthetic oil that creates an ionic bond between the oil and bearing parts for silky frictionless action INCLUDES: Four 18x12x4mm Bearings Four 13x6x5mm Bearings Six 12x6x4mm Bearings One 8x5x2.5mm Bearing Two 16x8x5mm Bearings Two 15x10x4mm Bearings Fourteen 11x5x4mm Bearings REQUIRES: Removing original bearings from kit JiM 3.22.07 ir/jxs