The FAMCO JPL25 Joist Pocket Liner 25-11 is used to create a pocket in concrete foundations for engineered girders, I-beams, and floor joists. Easily installed with use of preplaced nails. Designed with new construction in mind. Top knockout used for joist placement. The FAMCO JPL25 Joist Pocket Liner 25-11 is used for 1½ inch, 1¾ inch, 2 inch, 2-5/16 inch and 2½ inch wide x 11-7/8 inch tall floor joists. Sold only in 30 units per box. If you have any questions about the FAMCO JPL25 Joist Pocket Liner 25-11, please refer to the FAQs above or feel free to contact us by phone or email.