... :one year / 1800-2000 working hoursCrawler crane & Pile Drive Undercarriage parts---Track shoe, Pin, Bottom roller, Top roller, Sprocket, IdlerWhich we ... , Idler, Bottom roller, Top roller 2. Excavator and Bulldozer Undercarriage parts:Track chain, Track shoe, Sprocket& Segment, Idler, Track roller, Carrier roller ...