##Enduro ABEC3 6903 Wheel Bearing 17x30x7 (Single) Enduro ABEC3 6903 Wheel Bearing 17x30x7 (Single) features the bearing specialists high precision, Grade 10 chromium steel balls that are within 10/1,000,000″ round, twice as round as the industry standard. These precision balls ride in a 52100 high carbon chromium alloy race, hardened to R-62 to make them extremely tough and durable. Mirror finish polishing of the races creates ABEC-3 precision and noiseless movement. The bearing is labyrinth sealed with two NBR 70 full-contact, medium-high friction seals, which ride in a groove machined into the bearing. Combined with marine grease, this seal creates an almost impenetrable barrier to contamination.