As the muzzle end of the barrel is the last place to see the exit of the bullet, it is important to keep this area free from harm. When placed over the muzzle, these guides allow cleaning rods to go straight into the barrel while protecting the muzzle area. The rod passes thru an oilite bushing which is pressed into the Delrin body. The J Dewey Mfg Delrin Muzzle Bore Guides can be used with all types of cleaning rods. Some models have milled cuts to allow for sight clearance. Designed for the year-round shooter.