100 percent Cotton Bore mop made with a brass core. Mops can be used for quick cleaning and bore lubrication. Mops are especially excellent when using oil for bore lubrication because they create foaming action that helps in the lubrication process. 12 Gauge Mopster-10" Working Length Excellent for quick cleans between rounds for trap shooters and all shotgun sport shooters! Standard American Shotgun #5/16-27 thread