Inner frame uses large-sized vertical and horizontal pieces of material. Built-in blinds can adjust light passing through. Straight-axle design, can bear heavy weight, easy to install and disassemble. Outer frame can be 10 or 13cm wide. Inner frame can be fit with single-layer or multi-layer glass. Three sealing air-tight strips, superior sealing and air-tight performance. Stand-alone drainage hole. No-rear-button design. Large three-point interlinking handle.