Material : Steel, Nylon, POM, Rubber The independent material is steel The spoke wheel is nylon material to reduce the noice during sliding The floor guides,Anti-pads are POM Stoper 's half material is rubber -LRB- to reduce the noice when wheel hit with stops -RRB- Track had been pre-drilled 16 '' apart holes, can be for 16 '' apart studs wall Track 's two ends also pre-drilled pocket-size screw holes, pocket-size hole plugs will be offered The spoke wheel kit require at least 7 4/5 '' space from intensiveness of the door to the ceiling, pls check if you have sufficient space before order .