That is debatable. For the most part, Thyssen considers them interchangeable but the fact is the Finder relay's pins are at least twice as big as the Schrack's. And Otis has been installing non force-guided versions that have huge pins. The problems I have had have been from using the Schrack relays in the blue finder bases. The pins barely reach into the sockets. I would just worry you may have false negative results with this combo and if you use a Schrack base the sockets may get stretched out from the Finder relays and cause the same problem. Even though you get a Schrack relay no matter what part number you order from TK, there has to be a reason they used both bases on their tester. Just something to think about.