The BCW 33 1/3 record album sleeves are an acid free, archival quality product made of thicker, 4 mil crystal-clear polypropylene. Designed for use with both single and double LPs, these outer sleeves will help protect the jackets of your collectible 12-inch albums. Use with BCW 33 RPM Record Topload Holders for an extra layer of protection. 100 Sleeves per Pack.