This rare and unusual item is for an extremely old SGI machine. It was called the "Power Series" and ran MIPS 3000 and 4000 cpu's (Not 4400's even). They were refrigerator sized cabinets with removable drives. The Personal Iris also used these drive rails.
These rails were used for SCSI drives that could be removed from the system simply by pulling them out (after shutting the machine OFF first, of course) from the front of the machine. I only have the left and right rails plus the pull handle. No screws, nor the back metal bracket and cable that connected the drive to the system.
Price to you: shipping only! They are plastic, and thus quite light. I could probably send them first class at minimal cost. Worst case, Priority Mail is what, $4 these days?