Filter Filters Sierra Remove All Filters Price $100-$500 (131) $500 and above (7) Condition New (138) Brand Harmony Audio (138) Make GMC (138) 1999-2006 GMC Sierra Ext Cab Truck Harmony R124 Single 12" Sub Box & CXA400.1 $280.99 2007-2013 GMC Sierra Crew Cab Truck Harmony R124 Dual 12" Sub Box Enclosure New $241.99 2007-2013 GMC Sierra Extended Cab Truck Harmony R104 Single 10 Sub Box Enclosure $136.99 2007-2013 GMC Sierra Extended Cab Truck Harmony F104 Single 10 Sub Box Enclosure $154.99 2007-2013 GMC Sierra Extended Cab Truck Harmony R124 Single 12 Sub Box Enclosure $145.99 01-06 GMC Sierra Non-HD Crew Cab Truck Harmony A122 Dual 12" Sub Box Enclosure $255.99 1988-1998 GMC Sierra Ext Cab Truck Harmony F104 Single 10" Sub Box Enclosure $154.99 2007-2013 GMC Sierra Extended Cab Truck Harmony F124 Single 12 Sub Box Enclosure $169.99 1988-1998 GMC Sierra Ext Cab Truck Harmony R124 Single 12" Sub Box Enclosure $146.99 2007-2013 GMC Sierra Extended Cab Truck Harmony A122 Single 12 Sub Box Enclosure $160.99 1988-1998 GMC Sierra Ext Cab Truck Harmony R104 Dual 10" Sub Box Enclosure New $218.99 1988-1998 GMC Sierra Ext Cab Truck Harmony F104 Dual 10" Sub Box Enclosure New $229.99 01-06 GMC Sierra Non-HD Crew Cab Truck Harmony R124 Dual 12" Sub Box Enclosure $221.99 01-06 GMC Sierra Non-HD Crew Cab Truck Harmony A102 Dual 10" Sub Box Enclosure $249.99 2007-2013 GMC Sierra Crew Cab Truck Harmony A102 Dual 10" Sub Box Enclosure New $269.99 1999-2006 GMC Sierra Ext Cab Truck Harmony A102 Single 10" Sub Box Enclosure $159.99 2007-2013 GMC Sierra Extended Cab Truck Harmony A102 Single 10 Sub Box Enclosure $149.99 01-06 GMC Sierra Non-HD Crew Cab Truck Harmony F104 Dual 10" Sub Box Enclosure $239.99 123456