Rail Depth Adapter Kit for Racks 4in 1UThis depth adapter kit lets you extend or reduce the mounting depth of one rack unit (1U) in your server rack by up to four inches. If you're using the adapter kit in a two post installation the extenders can support a total weight load of 10 lbs. (4. 5 kg). If you're using the adapter kit in a four post installation, the extenders can support a total weight load of 90 lbs. (40 kg), you can even use two sets of extender brackets in a four post