Fits Chevy Silverado / GMC Sierra 1988-1998 Extended Cab Jack Must Be Removed Down Firing Design - Fits Under Rear Seat Hole cutout for 8" Sub: 7 1/8" Hole cutout for 10" Sub: 9 1/8" Subwoofer Mounting Depth : 5.25" Mounting Depth based on 6.00" diameter magnet Subwoofer Airspace: Approx. 0.75 cu. ft. Per Sub/Side Made with 0.625" MDF 1.25" Clearance Under Box Speaker Wire Terminals: 1 Per Subwoofer Box Type: Sealed Box Box Finish - Carpet Subwoofers & Amps Not Included Hole Cutouts adjustable per request Subwoofer Mounting depth based on the most common size subwoofers. Some Subwoofers with oversized framing/magnets may not fit without modification. If you're using a subwoofer that is close to the max specs please contact us for fitment confirmation.