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" electric drill. Each unit comes with the brush, 36" extender rod and a plastic guide sleeve to augment insertion through tank necks. Heavier, stiffer wire from bottom flash rust or other deposits in STEEL tanks. Not recommended for Aluminum models. Order #43046 for replacement brush only.