Bottom Brush - Heavy Duty Includes: Brush Aluminum Rod Special, small stainless brushes for removing those stubborn deposits on the very bottom of dive tanks. Each brush screws onto a 3 - foot aluminum rod which fits into a 3/8" electic drill. Each unit comes with the brush, extender rod and a plastic guide sleeve to augment insertion through tank necks. Heavier, stiffer wire from bottom flash rust or oth deposits in STEEL tanks. Not recommended for Aluminum models.