This listing is for a custom enclosure built specifically for 2 12" Sundown Audio X-12 subs. We use 3 4" aeroports to reduce port noise so you get nothing but clean clear bass from your sub. Also, the subs are recessed 3/4" into the box. We use an internal brace as well as a double top baffle. All joints are glued and screwed together to insure that the box will hold up against the high output of the subwoofers for as long as you need it to.