Rockville 12" Bedlined Sub Box For 1999-06 Silverado 1500 Xcab/99-06 GMC Sierra Rockville 12" Sub Box for 1999-2006 Chevy Silverado 1500 Xcab/99-06 GMC Sierra. Proudly Made In The USA, Using Only The Finest Quality Materials - For The Best Level of Performance From Your Subs! 5/8" USA Heavy Duty MDF Construction. Machine precision cut mounting holes . True Bed Liner Finish. High quality Screw down spring loaded terminals. Designed, tested, and engineered to work with most of todays popular woofers. These enclosures are built with the quality additives needed to maximize the performance of any sound system. Enclosure Measurements: Type of Enclosure: Sealed. Enclosure Sub Size: Dual 12". Dimensions in Inches: 9.5" L x 51" W x 15.25 H". Mounting Depth: 5 (inches). Mounting diameter (hole size): 11 (inches). Wood thickness: 5/8 (inch). Air Space: 0.95 Cubic Feet. Material: Highest-grade MDF wood on the market.