... :Wood plate, cannot bear heavy body, no damp-proof, bad mothproof, and bad fireproof.Or, hollow metal frame, weak, proteiform. 2. ... by chain, strong, slip resistance. Other Brand:Steel wire, bad slip resistance, can not drive too much, motor easy to ... transformer, which is harmful to human body. 6. Photoelectric SensorPhotoelectric sensor makes roller pause at correct position. Press one button to ...