If you have a GSG-5 .22LR rifle and want to add a real suppressor, fake suppressor or muzzle brake, let us do the work for you!. Since the barrel diameter is too small to thread it 1/2x28, we will thread your barrel in the smaller size metric thread of 8mm x .75mm making it easy to thread on one our adapters with its own thread protector. You ship us your barrel with only the trunion/ feed ramp installed, we do the work and you pay return shipping, & insurance of $23.99. Call with any questions.*New thread Protector is shown in last photo.