Powerglide Large Piston and Steel Drum. Steel drum with 29% more piston apply area! This billet aluminum piston delivers the most clamping force available today. Features Include: Large piston made from 6061 T6 billet aluminum. 9 or 10 plate design. Dual apply feed slots. 100% drop-in assembly. Also available as a complete kit. Part # K743920SH.