Visual mirror: It is used to observe a series of technological production of liquid or reactant inside the container on the fixed container such as tank and reaction kettle. Sanitary equipment is more common. The materials are 304 and 316 stainless steel. The nominal pressure range is 2.5 and 6 kg/cm 2. Working temperature: Metal below 200 C, plastic below 80 C, allowable rapid change temperature 80 C; nominal diameter range of 15 ~ 150 mm, individual specifications to 200 mm. There is no formal product for glass tubes in glasses with nominal pressure of 6 kg/cm 2. If selected, trial production is required. Glass is made of toughened glass with a maximum temperature resistance of 200 C.