These rack ears are used to mount half-rack sized Shure equipment such as the ULXP series of microphone receivers, and similar Shure SCM series half-rack sized microphone mixers.
UA506
has a short rack ear #53E8484 (1.1 inch wide) and a long rack ear
#53F8484 (9.7 inches wide.) These attach to a ULX receiver (8.5 inches
wide). Total width is 19.3 inches.
I can include a screw of the appropriate size and type to mount these rack ears for reference, but I do not have a full set of screws for this kit. The screws can easily be found at most local hardware stores, and should be no more than 3/8" in length. 8 screws are required for each kit (4 per rack ear.)