Roller made from Special Heavy Duty Polyurathene. Best Quality Ball Bearing used to mount Roller to ensure smooth rotation. For tight Grip each Roller is supported on Pivoted Rocker Arm. For ensuring required flexibility each roller is loaded on Spring. Features Smooth & relaxing Ride. Absolutely low Power Consumption. Freedom from disturbing Noise and Vibration. Auto-adjustment on Guide Rails. Liberation From the Problem of Oil and Grease Sticking on Rails and accumulation of same in Pit. Therefore low chances of problems arising from it. It is also Cost Effective.