I was trying the fixed cup as if it were French threading, but regardless the adjustable cup won't move. The worst adjustable cup I've ever had to unscrew was still "easy"...this one is seriously frozen. And your post made me think to actually clean off the faces and look at the threading (duh)...which is 1.37. They're Shimano cups. The lockring threads onto Japanese adustable cups just fine. Loctite maybe?