This listing is for a 37/64 x 28 or .578 x 28 Threaded barrel protector. It is machined from stainless steel to very high quality standards on CNC lathes in my shop. It is counter bored to accommodate barrels that are not undercut at the shoulder. Length is .460" Outside diameter is .730 With a great looking machined grooves. Fits Aftermarket Threaded Barrels with a 37/64 x 28 or .578 x 28 tpi right handed thread. Will not fit the factory Glock since it has a left hand metric thread. Please confirm your thread size before ordering!