Answered: Pneumatics

if i bought the single acting pnumatics would i be able to buy a douple acting one and connect it

To drive a double acting cylinder, you need a double acting solenoid.
The Vex double-acting cylinder kit includes one of these.

If you initially purchase a Single Acting Cylinder kit (Kit 1) you could then later add on a Double Acting Cylinder Add-On (Kit 2A).