It has 45 degree tilting stainless steel shards which can effectively prevent the rain from flowing back. It has a dense mosquito net with a stainless steel filter at the to keep mosquitoes, dust and other debris out. It features a clip-on attachment ring. Three fixed snap rings at the grip prevent loss of cover. The hood has its own barbs. Please kindly disassemble it slightly before installation, and it is automatically fixed when inserted into the hole in the wall. It has a beautiful and durable spherical external outlet. Special functions: air evacuation / rainproof / breathable. Size (diameter ): about 7.5cm; 8cm/3.15inch; 10cm/3.94inch; 12cm/4.72in; 15cm5.91in; 18cm/7.09in; 20cm/7.87in; 30cm Product Description Size:15cm Product Information: Material: 304 stainless steel Size (diameter): about 7.5cm; 8cm/3.15inch; 10cm/3.94inch; 12cm/4.72in; 15cm5.91in; 18cm/7.09in; 20cm/7.87inch; 30cm Special functions: air exhausted / rainproof / breathable Application: installation outside