...The two front hubs are made of Titanium while the one rear is made of Steel https://pbase.com/slidevalve911rsr/image/67998402

Now you can compare the factory Front Titanium unit https://pbase.com/image/67998410 to the Steel reproductions https://pbase.com/slidevalve911rsr/myrsr_suspension_centerlocking_hubs_front

Compare the factory Rear Steel unit https://pbase.com/slidevalve911rsr/image/67998405 to the Steel reproductions https://pbase.com/slidevalve911rsr/myrsr_suspension_centerlocking_hubs_rear

Note the longer threaded shaft https://pbase.com/slidevalve911rsr/image/67998418 on one of the two front hubs. Also, the 'flange' on one of the front hubs is slightly thicker than the other https://pbase.com/slidevalve911rsr/image/67998420 - Not an exact matching pair but the differences are not significant...

Go here to see all these components installed https://pbase.com/slidevalve911rsr/image/56767813 Very 'trick' looking!