1/2 x 28 Threaded barrel protector. It is machined from US made steel to very high quality standards on CNC lathes in my shop. It has a durable black oxide finish. It is counter bored to accommodate barrels that are not undercut at the shoulder. Length is .460" Outside diameter is .630 With a Great looking splined surface. You will not find these anywhere else! Fits Threaded Barrels with a 1/2 x 28 tpi right hand thread. Please confirm your thread size before ordering.