Ruger 10/22 Rifles with a .600 long barrel threads require the use of a spacer to reduce the threads to the .400 thread length needed when using a suppressor. This prevents potential baffle damage from threading a suppressor too far on the barrel. It also prevents the barrel threads from protruding into the suppressor chamber, eliminating carbon buildup on the barrel threads that make the suppressor hard to remove. This spacer was designed by Ruger engineers to precisely fit 10/22 barrel threads. It maintains concentricity between the barrel and suppressor and threads onto the barrel to keep it from falling off when the suppressor is removed. It also creates a solid, square surface when mounting the suppressor. The spacer flats make it easy to install and remove the spacer with a standard wrench. Made from durable steel with a black oxide finish.