Rack attachments will fit any rack with matching tubing and hole size to the intended rack. If Rack A has 3-by-3-inch uprights with 1-inch holes, Rack A’s attachments will only fit Rack B if it has 3-by-3-inch uprights with 1-inch holes. In this specific case, we likely see compatibility from Rogue Monster Lite to Rep PR-4000, as well as Rogue Monster to Rep PR-5000.