The ar-style bore guide slides in place of the bolt carrier group assembly while cleaning.This centers the cleaning rod while preventing solvent from entering the upper receiver and trigger mechanism.The ar15/m16 style bore guide can be used for all of the ar15/m16/m4 family of rifles.Will work for both 5.56mm/223 cal.Variants.Pro-shot's bore guides are manufactured using delrin.Delrin is chemical resistant and will stand up to harsh chemicals providing continual use.Thread Pattern: N/AType: Bore GuideSize: 223/5.56 NATOQuantity: 1Bristle Type: NoneMaterial: DelrinTip Feature: O-RingProtects: Bore During CleaningSuitable For: 223/5.56mm RiflesEco-friendly: Yes