This article introduces the manufacturing process, material selection, sealing characteristics, and sealing advantages of a new hollow metal C ring used in Stirling cryocoolers. Given the high leakage rate and ease of failure of rings made of traditional rubber, PTFE, and solid silver wire, the manufacturing accuracy of the metal C-type sealing ring is high. After years of testing, use, and demonstrations, the metal C ring has achieved high reliability and a low leakage rate under conditions of strong impact and radiation resistance. The leakage rate of the metal C-ring can reach to 10-9 atm.cm3/s.m, which meets the leakage rate requirements of Stirling cryocoolers.