The Santa Fe CrawlGuard Felt Underlay 5 ft. x 50 ft. is an optional crawlspace underlay that functions as an effective protector of the CrawlGuard Liner. It secures the vapor barrier from sharp objects like pointed stones or broken concrete. To set it up, the underlay must be installed between the CrawlGuard Liner and the ground. Product is highly recommended for use in storage or high traffic areas. The roll weighs 20 pounds and its size is 5 ft by 50 ft. Covers 250 square feet area.