Otis brushes last longer than most with their superior construction and engineered features. The brushes have a precision thread with no weak undercut. Their Tufcor proprietary core wire resists corrosion and their tight twist insures better bristle retention. They can be used with all firearm cleaning chemicals. They have twice the fill as other brushes. The stem is cold welded to the core and the brushes are filled to the end. Each brush has the specific caliber or gauge stamped on the stem so you can avoid cleaning your gun with the wrong brush.Works in most .22 and .223/5.56 caliber rifles.