The MTM Bore Guide – Large, Black assures perfect alignment of a cleaning rod to the bore, prevents solvent contamination of magazine and trigger mechanism, and protects a rifle’s finish. If you’re serious about cleaning your rifles these are a must! Catalog No. BGR-S-40 for 17 to .243(6MM) calibres. Fits Remington 700, 788, 40X short actions; Mauser 300, Ruger 77 short actions; and similar bolt sizes.