##Enduro ABEC3 6901 Wheel Bearing 12x24x6 (Single) The Enduro ABEC3 6901 Wheel Bearing 12x24x6 (Single) 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. High precision, Grade 10 chromium steel balls 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. When replacing a bearing, measure the inner diameter (ID), outer diameter (OD), and width (W) to determine compatibility.