The component of Air Inlet 

Windows: Plastic contains the anti-ultraviolet raw material, making it longevity   Protection Net: Reasonable structure, material is Polypropylene. 

Return Spring: High quality stainless steel spring, durable and rustless. 

 Pulley Accessories: Rigidity hard drawn wire round steel, ensuring accurately opening. Rigidly connected will not be stretched, the surface is treated by galvanization in case of rust.