Dual 12-inch Sealed Car Sub Box Made with 3/4" MDF and lined w/Polyfil (2.46 cu ft Airspace - 12SQB). You've got an awesome subwoofer there, pal. But where's it gonna go? You can't just throw that thing in the trunk and call it a day. Don't worry, Belva's got your back. With superior construction, great features and everything you need for bass, you'll be ready to pass up that entry-level box you've been eyeballing. Belva Subwoofer Boxes are CARB Phase 2 Compliant You get quality boxes with solid 3/4" MDF because nothing else will do the job right. You want to flex your windshield, not your box's innards. You get polyfill built into the box, making sure your subs perform perfectly. On top of that, you get a box that's CARB Phase 2 Compliant, meaning your box won't emit as much nasty formaldehyde as the competition. Better for your bass and better for you.