BTL 12 BW SRNovember 13, 2015 | By Btl Liners A 12-mil string reinforced cover or tarp material. Can be used as a hay or grain pile cover. Most commonly used in light deprivation systems. share forward print Leave a Reply Cancel replyYour email address will not be published. Required fields are marked *CommentName * Email * Website Save my name, email, and website in this browser for the next time I comment.