Sig Sauer Piston, 1/2 x 28 RH, 9mm, Fits SRD9 SRD-PISTON-12X28 Convert your SRD9 or SRD45 suppressor to a 1/2x28 Right Hand thread pitch with the SRD-PISTON-12X28. The piston is made of 17-4 heat treated stainless steel with a matte glass bead finish. The piston will fit a variety of hosts" and it is a perfect choice for converting your SRD45 to 9mm. Simply swap the conversion piston with the original piston in your suppressor to match your barrel thread pattern.