ASC Chevy Silverado or GMC Sierra HD Crew Cab Truck 2001-2006 Dual 12" Subwoofer Custom Fit Underseat Sub Box Speaker Enclosure Dimensions: Width 48" x Height 6" x Depth 16-3/4" Install Location: Under Rear Seat Install Notes: Rear seat must be able to fold forward for box to fit Mounting Depth: 4-1/2 Inches Air Space: 0.48 Cubic Feet