Trampoline tube are hot galvanize outside and inside. it is stronger. can use many years. Oval Trampoline tube are hot galvanized steel frame, galvanized inside and outside, it is strong, withstands hard jumping and can be used for years- W shape legs base- Frame pads (PVC and rubber cloth), inside EPE foam material, high density, closed-cell foam, not absorb water, lose shape and mildew- ...