High Impact & Waterproof Material; a medium density polyethylene is used which gives high impact strength at low temperatures yet is very tough and resilient at ambient temperatures. The polyethylene used by Hardcase will not absorb moisture and it is resistant to most common chemicals and oils. The Overlapping Compression Design can cover various depths with one case. High density 0.4" thick closed cell expanded polyethylene foam with heavy duty adhesive backing is used to give good, compressive grip to keep the drum in position and resists wear and tear. A chosen wheel design with polypropylene center and a gray rubber outer tire giving great strength, good grip and quiet rolling. Wheels applied on bass drum cases.