This Flat Idler Pulley works both as an OEM replacement and as a general purpose pulley for power transmission such as compressors, industrial fans, lawn mowers, snowblowers, and electric motors. It does not come with a bore adapter installed, the inside diameter is equal to the bearing diameter of 17mm. 31300120 features a heavy duty sealed radial single-row bearing.This part is Painted Black to prevent rusting. Additional Features: Made of Steel Flanges angled outward to help increase belt life Direct OEM Replacement for: Hustler Big Dog: 601162