The JP Cleaning Bore Guide is a lathe-turned piece of aircraft grade, color anodized aluminum with heavy duty O-rings to center and retain it in the upper receiver while cleaning through it. It is made with a solvent hole located at the ejection port. It will avoid damage to the chamber, throat, and crown of your expensive rifle.FeaturesAircraft grade aluminumFor Use with the Following Calibers: AR-10 or SR25 rifles in 243 or 308 Caliber.Rod features heavy-duty O-rings to center and retain it in the upper receiver while running the cleaning rod through it.Rod also has a hole for solvent centered in the receivers ejection port. This tool keeps the user from damaging the barrel by improper cleaning. Approximate length is 11-1/2"