what are they? i was considering this option as it will allow for a smaller box

It think it's mostly for show. You gotta expose those huge magnets while they deliver bass surges. :P

The important thing is that the front and back side of the subs must be isolated from each other. The front side makes sound waves as it vibrates, and also the back side, but produces the opposite signal. Exposing them to each other will make wave cancellations, thus, weaker sound.

Please someone chime in to correct me...

For subs, it really doesn't matter which way you mount them, from an SQ perspective. Do which ever one you like or best meets your requirements.

And yes, the most important thing is to isolate the front & rear output from one another, to avoid cancellation by the out-of-phase signal.

what are they? i was considering this option as it will allow for a smaller box

Theres no real pros and cons..

Pros yes you do require less airspace because you invert the sub so you dont need to worry about compensating for it.

my subs are inverted because when i installed them the right way they would not bass.. i dunno why so i had to invert them.. btw i have audiobahns. yea not the bess but still basses..lol

either you wierd they wrong... or air space to little

i personally find an inverted sub to be more flashy. when i redo the trunk with fiberglass, i'll be inverting my w6v2's. there are some subs that are just plain ugly inverted though... make sure those cages look pretty!

i have three 12" kicker l5 inverted in my truck (with a mirror and some other toys, this trunk has alot of room)
i inverted mine to get just enough airspace
not to mention it looks cool

con: harder to clean?? i dunno...

with my sub when I inverted it the notes seemed to be deeper i.e. more airspace but I agree there aren't really pro's and cons its what you prefer... on fair warning if your sub is heaver than your box and your box is not anchored down and the sub is inverted... well you get the idea haha... off topic anyone interested in a Powerbass XA3000D amp? :P I blew my 13w7 with that amp with the level/gain half way. sorry back on topic...

Deffinet pros and cons to all of this.

Pros: You can be more open with your enclosure design. If you have a deep mounting sub but dont have the room to have a deep box, you can make the box wider to get the correct airspace and make it very shallow, invert the sub and you wont have to worry about mounting depth.
It looks awesome!!