ASC Chevy Silverado or GMC Sierra Full Size Extended Cab Truck 1999-2006 Single 12" Subwoofer Custom Fit Sub Box Speaker Enclosure Dimensions: Width 23-1/2" x Front Height 9-1/2" x Rear Height 7" x Depth 13-1/2" Install Location: Under Rear Seat (Passenger Side) Install Notes: No Modifications Required Mounting Depth: 6 Inches Air Space: 0.90 Cubic Feet