Dry slide rails designed for full length servers typically have excess inner rail in the back. Since the R210 and R240 are shorter servers, the inner rails of this kit can be shortened so that they will fit within low depth racks. Unlike OEM Dell rails, these will work with square, round or threaded hole racks out of the box. The rail is made from 18 Ga galvanized steel for long-lasting, high-quality experience.