Filter Filters Sierra Remove All Filters Price $100-$500 (176) $500 and above (19) Condition New (195) Brand Harmony Audio (195) Make GMC (195) Compatible with 2001-2006 GMC Sierra HD Crew Truck Harmony F124 Dual 12" Sub... $526.99 Compatible with 2001-2006 GMC Sierra HD Crew Truck Harmony A122 Dual 12" Sub... $410.99 Compatible with 2007-2013 GMC Sierra Crew Cab Truck Harmony R104 Dual 10" Sub... $308.99 Compatible with 1999-2006 GMC Sierra Ext Cab Truck Harmony A122 Single 12"... $396.99 Compatible with 2001-2006 GMC Sierra 1500 Crew Truck Harmony F104 Ported 10"... $234.99 Compatible with 2001-2006 GMC Sierra HD Crew Truck Harmony R124 Dual 12" Sub... $326.99 Compatible with 1999-2006 GMC Sierra Extended Cab Truck Harmony A122 Single... $310.99 Compatible with 2007-2013 GMC Sierra Ext Cab Truck Harmony A122 Dual 12" Sub... $481.99 Compatible with 2007-2013 GMC Sierra Crew Cab Truck Harmony F124 Dual 12" Sub... $450.99 88-98 GMC Sierra Ext Cab Truck Harmony F124 Dual 12" Rhino Sub Box & CXA800.1 $531.99 Compatible with 2007-2013 GMC Sierra Crew Cab Truck Harmony R124 Dual 12" Sub... $336.99 01-06 GMC Sierra 1500 Crew Truck Harmony F104 Ported 10" Sub Box Enclosure $134.99 88-98 GMC Sierra Ext Cab Truck Harmony A122 Dual 12" Rhino Sub Box & CXA800.1 $541.99 Compatible with 1988-1998 GMC Sierra Ext Cab Truck Harmony A122 Dual 12" Sub... $516.99 Compatible with 1988-1998 GMC Sierra Ext Cab Truck Harmony A122 Single 12"... $396.99 Compatible with 2001-2006 GMC Sierra HD Crew Truck Harmony F124 Dual 12"... $465.99 Compatible with 2007-2013 GMC Sierra Crew Cab Truck Harmony A122 Dual 12"... $455.99 1999-2006 GMC Sierra Ext Cab Truck Harmony R124 Dual 12" Sub Box Enclosure New $247.99 2007-2013 GMC Sierra Ext Cab Truck Harmony R124 Dual 12" Sub Box Enclosure New $217.99 2007-2013 GMC Sierra Ext Cab Truck Harmony A102 Dual 10" Sub Box Enclosure New $235.99 2001-2006 GMC Sierra HD Crew Truck Harmony A122 Dual 12" Sub Box Enclosure New $255.99 2007-2013 GMC Sierra Crew Cab Truck Harmony A102 Dual 10" Sub Box Enclosure New $269.99 2001-2006 GMC Sierra HD Crew Truck Harmony F124 Dual 12" Sub Box Enclosure New $270.99 01-06 GMC Sierra 1500 Crew Truck Harmony R104 Ported 10" Sub Box Enclosure $115.99 123456...9