Machined from a special copper-free alloy that's as gentle on the bore as brass, while it eliminates false indications of blue copper fouling on the patch. Holds the patch tight in two places, doubling the effective cleaning area. Reverse taper self-guides into bore. SPECS: Proprietary copper-free alloy. Approx. 21?4" (5.7cm) long. .17 cal. - 5-40 male threads. .22 & .30 cal. - 8-32 male threads. Mfg: Bore Tech