Powerglide Large Piston & Steel Drum. Steel drum with 29% more piston apply area! This billet aluminum piston delivers the most clamping force avaiable today. Features Include: Large piston made from 6061 T6billet aluminum. 9 or 10 plate design. Dual apply feed slots. 100% drop-in assembly. Also available as a complete kit Ò Part# K743920SH.