The universal 4POSTRAIL kit can be used with 1U, 2U, and 3U equipment up to 231 pounds ADJUSTABLE RAILS: Extend from 18.5 to 29 for proper fit with various sizing requirements 4-POST MOUNTING: Secures equipment at both the front and back of the rack ATTACHMENT HARDWARE INCLUDED: 16 M5 x 12 screws are included to secure the rails to each post LIMITED 5-YEAR WARRANTY