Hard seal refers to a sealing structure in which both sides of the sealing pair are made of metal materials or other harder materials. Hard seals use seals made of hard materials (such as metal) to tightly connect the contact surfaces between the two parts to form a reliable seal. These seals are usually gaskets, O-rings, packings, etc. For example, the full-function ultra-light regulating valve has wear-resistant alloy protection for sealing, high reliability, and a leakage rate of 10-7. It can already meet the requirements of the cut-off valve. The cut-off valve requires sealing performance, and the leakage of the soft seal valve is the lowest. The cut-off effect is of course good, but it has the disadvantages of not being wear-resistant and unreliable. From the dual standards of leakage and sealing performance, hard seal cut-off is better than soft seal cut-off.