Ox-Yoke muzzleloaders Black Out Flush Cleaning System. For use with 6.75mm nipple threads. Easy, neat, clean, effective & economical. Give your rifle a traditional hot water wash! Nothing could be easier or more effective than the flush, pump action hot water wash. The flush system comes with a brass nipple attachment, hose, cleaning patches and Wonder Lube 1000 treated patches to protect your rifle until the next use.