idler pulleys are made of nylon or UHMW material.they are black or white.They may be pulleys, sheaves,rope sheave,or idler wheel plastic idler pulley Used for Windows, Door, Transportation Mechanical Device, Trolly, Toy, Trunk, Elevatorplastic idler pulley Features and Benefits :Self lubricatingHigh tensile strengthCorrosion and chemical resistanceExcellent impact resistanceExcellent vibration ...