1/2 x 28 tpi to M11/9 Adapter -If you have a 1/2 x 28 tpi threaded barrel and want to use an M11/9 (or M10/9) suppressor with 3/4 x 10 threads, this adapter will provide the conversion without the expensive cost to replace or re-thread the barrel.TROS adapters are manufactured from 300 series stainless and are black oxide coated. They are guaranteed to be concentric.