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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.
UA507 has two short rack ears #53E8484 (1.1 inch wide each.) These attach onto two ULX receivers (17.0 inches wide). Total width is 19.2 inches. ULX receivers are fastened together with metal link bars.