gravity roller, heavy duty, hex shaft gravity roller, land roller with heavy duty. 1. application: airport gravity conveyor, pallet conveyor, heavy duty conveyor2. roller diameter: 50, 60, 63.5mm...3. roller length: 500, 600, 700 as customer requirement4. shaft: 12, 15, 17.5, 20mm...hex shaft or round shaft5. material: zinc steel