The base waterproof layer is often constructed using a composite structure of PVC and sponge. Patented EP003 technology utilizes a three-layer composite process: an outer PVC layer ensures waterproofing, a middle sponge layer enhances cushioning and toughness, and an inner PVC layer prevents structural deformation. High-end products use environmentally friendly PEVA material, which is both lightweight and biodegradable.
Patent CN004, issued in 2024, discloses an elastic cord fastening system. This system replaces traditional elastic bands with a disc-type clamping structure. It utilizes a polyester fiber braid with a silicone anti-slip layer, ensuring stable retention even in force 5 wind tests. The cap body is typically constructed of 0.8mm thick transparent rubber, boasting a light transmittance of 92% and a tear resistance of 18MPa.