This Flat Idler Pulley is for use as a general purpose pulley for power transmission such as compressors, industrial fans, lawnmowers, snowblowers and electrical motors. It does not come with a bore adapter installed, the inside diameter is equal to the bearing diameter of 5/8''. 31300075 features a heavy duty sealed radial single-row bearing.This part is Zinc-coated for long-term rust prevention. Additional Features: Made of Steel Flanges angled outward to help increase belt life