This Odessa Piston M13.5×1 L is for 13.5×1 LH thread pitch barrels to use the Odessa silencer, The Odessa Silencer comes with a 1/2×28 piston.
It was founded by Mike Pappas, and if that name rings a bell, it’s because Mike co-founded another silencer company back in 2008. Among others, Mike is also teamed up with silencer designer Todd Magee. Mike and Todd have set out to build the best suppressors on the market. There is no substitute for experience.