31" Universal Rackmount Rails are designed for deep Server Racks. These Rackmount Rails can be installed into racks with square, round, or threaded holes. Rack Mount Equipment weighing up to 200 lbs (90.7 kgs) can be installed using Rackmount Rails. The Rackmount Rail is 30.6" (777 mm) deep and can be installed into Server Racks with installation depths up to 39.5" (1003 mm). Adjustable Rack Rails and Square Hole Mounting The rail kit depth is fully adjustable from 10"-31.75" (254mm-806mm) all by loosening the screws and nuts. The rail kit is made from 18 GA steel and is zinc plated. The RackSolutions Universal rail kits are square hole to allow for the rails to be compatible with round, square or threaded hole racks.