This is a optional XRAY 34 Tooth Differential Pulley with included Labyrinth Dust Covers, and is intended for use with the XRAY T1 and T2 Family of vehicles with ball differentials. The pulley features XRAY invented and patented "Labyrinth Dust Covers", special anti-dust protective covers that are great for keeping dust and dirt out of the diff. Each pulley uses 12 diff balls.