Amazon.com: 1999-2006 Silverado/Sierra Extended Cab Dual 10 Downfire with Amp Space Sub Box : Health & Household
Dual Sub Box (behind rear seat) 2001-2006 SILVERADO CREW HD - SSA STORE
2003-2006 CHEVROLET SILVERADO 1500 CREW Triple sub box - SSA STORE
Chevy Silverado Standard Cab Sub Box GMC Sierra Standard Cab Sub
2001-2007 Chevy Silverado 2500Hd Crew Cab Dual 12" Stereo Subwoofer Sub Box New - Walmart.com
JL Audio Stealthbox® (2003-2005, Dark charcoal) Driver side custom-fit enclosure with 10" W6v2 subwoofer Fits 1999-2005 Chevrolet Silverado / GMC Sierra Extended Cab (with full-bench rear seat) at Crutchfield
DUAL SUB BOX for 2003-2006/07 Classic Chevy Silverado 1500 CREW - Sound Off Audio, Inc.
Amazon.com: Compatible with 1999 2000 2001 2002 2003 2004 2005 2006 Chevy Silverado Ext Cab Truck Alpine S-W10D4 Type S Car Audio Subwoofer Custom Single 10" Sub Box Enclosure Package : Electronics
Ported sub box 2007-2013 Chevy Silverado Extended Cab truck