This listing is for a custom enclosure for a DC Audio Level 3, 4, 5 or 6 Subwoofer. We use 3" aeroports to reduce port noise so you get nothing but clean clear bass from your sub. Also, the sub is recessed 3/4" into the box. All joints are glued and screwed together to insure that the box will hold up against the high output of the subwoofer for as long as you need it to.