In team update #3, it clearly say that
"Many of you have asked about the number of cylinders allowed on the robot. The correct number is 5 NOT 7 as perviously stated on the message boards.
The 4 additional cylinders that can be ordered are FREE. Even UPS freight is FREE. Airfreight will be billed to either a credit card or shipping account number."
You may only order the cylinders in the FIRST Custon Cylinder order form. The Bore sizes are only 3/4", 1.5", and 2" diameter, and stroke length ranging from 1/2" to 12".
You can find the related documents @
http://www.usfirst.org/robotics/doc_updt.htm
for the pneumatics manual and team updates.