Pro-Shot's Dual purpose design chamber mop can clean and lubricate both the chamber and locking lug recesses of your AR15/M4/M16 platform rifle. The longer smaller part of the mop reaches the chamber area, while the larger diameter is meant to reach the star chamber/ locking lug recess area. Excellent for use after bristled chamber brush for removing excess carbon fouling or excess CLP during the cleaning process. 100% Cotton Construction with Brass Core Support Ring under second area of mop for superior Star Chamber Cleaning Mops can be used for quick cleaning and lubrication Precision American Standard #8-32 threads Made in USA