M11/380 to M11/9 Adapter - If you have an M11/380 (which is factory threaded 5/8 x 11 tpi) and you want to use an M11/9 (or M10/9) suppressor threaded 3/4 x 10 tpi, this adapter will provide the thread conversion without the expensive cost to replace the barrel.TROS adapters are manufactured from 300 series stainless and are black oxide coated. They are guaranteed to be concentric.