The adapter is a direct replacement of the original plastic front sight and will fit over a non-threaded 15mm diameter barrel.
Please, note the thread is 1/2" UNF !
Fitting instructions: Undo the grub screw of the front sight and try to twist it, if it does not move, use a piece of wood and knock it out. Replace it the new adapter and fix it with the grub screw, which is plastic and will not leave a mark on the barrel.
You can contact me for advice on matching silencers.
The body is 3D printed plastic reinforced with carbon fibre, but the thread is metal.
A thread protector is included.