They used a D49 cylinder with some recommended changes from Motion Controls for their robot, SubZero. Dual onboard CO2 bottles were used for power - looks like it did the trick.  

They placed third in the competition, 120# class, They said they should have had 1st or 2nd, but there were some bad calls by the referees....

The Motion Control pneumatic cylinders will be doing battle again soon, June 16-18 in San Francisco at ROBOlympics, www.combots.net
 

SubZero specifications
● Middleweight Battlebot
● 120 pounds
● wheel chair motor drive
● 36 volt Nickel metal hydride battery pack
● top speed 9mph
● weapon system is a CO2 powered flipper
● two 20oz CO2 tanks
● high flow direct feed system so the pneumatic ram runs at 850psi, cylinder is filled in 0.2 seconds
● ram is 2.5" dia, 4" stroke, slightly modified for reliability:
added steel sleeve and bronze bushing, plus aircraft grade thru bolts were added along with a steel pivot base
● system is capable of chucking a 120 pound opponent 4-6 feet into the air
● front and side armor is 0.14" - 0.28" grade 5 titanium
● fight record is 19-6

Builder/weapon operator   Jerry Clarkin
Driver                             Jon Durand

For more information about the tournament go to www.r3rampage.com or www.battlebots.com

Go here for the SubZero website