shallow depth subs!

I need to install some subs into a very very small space, and need ideas on what subs have the smallest possible sealed box volume allowable.  The size of teh subwoofer doesnt matter, even willing to go with something weird like 6" midbass drivers, just spit some ideas my way.  Thanks

What is your size limitation based on? What is the maximum allowable depth, width, height, for example you have 14"in height and width so you can fit a 12" sub, but you only have 4" of depth, so the sub is too deep. What vehicle is the sub system for and where abouts in the vehicle.

I really need to know if there is a sub out there 8" or bigger that can work in a sealed box with a volume of less then .45 cubic feet