So I just acquired some slightly used GT3 controls arms. However, it looks as though the ends are OEM monoball type. Not the inserts. Not the aftermarket. But, OEM monoball. In the attached pic you will see the OEM GT3/ Cup car ends versus the monoballs. Possibly GT3 RSR?

 

Compare the length of the arms to the stock ones. Not all the cup arms will work on the TT depending if they are 997 or 996 due to variation in length, front, rear, etc. Make sure you have the 996 versions. Only the cup arms came standard with monoballs and solid adjustable thrust bushings. If you have rubber in the thrust bushing then someone added the monoball ends to the GT3 arms. Several aftermarket companies make the monoball ends. Check their condition carefully for any play. They should be very tight.

 

These are tight like new. The arms and ends are OEM 996 Porsche part numbers and not modified. The 996 control arms (RSR/Cup etc) are all compatible with each other from my research. The 997 are not though. The main outer arms are stock 996 GT3 arms. The inner monoballs are the ones that are the mystery parts. The inner monoball end is PN: 99634154195 which I cannot find anywhere. I assume them to be Porsche Motorsport only parts. From what I found so far, the 996 GT3 cup came with rubber inner arm ends. Supposedly many were upgraded to other parts.