mines a 3.5". Not sure of actual other measurements, never measured it, but its not the standard intercooler, its a 2 in and 1 out to accomodate for the twins.

 

i didn't go A2W because i didn't want all the extra stuff... however I may eventually go meth, how much i inject will be up to me tho...it works great and is safe. if you need to know anything about it contact Julio at AlkyControl (on here) or FROST THANKS BUNCHES GUYS FOR ALL YOUR INFO!!! and time on the phone!!