Sorry for the confusion:
Solenoid: SY3240-6H
http://www.pneuaire.com/sy3240-6h.html
Manifold: SY3000-27-1T (Mandatory)
http://www.pneuaire.com/sy3000-27-1t.html
For every solenoid you need one manifold (unless you buy a one gigantic manifold). So both are necessary to make a double solenoid work.
-RC