I guess you don't know which eyelets it has until you get it in your hands. As expected the top eyelet is 16mm with a brass reducer that makes it 15mm on mine. I used a Fox mounts as well.This is strange, as mine use normal Fox bushings top and bottom. 15mm that is. Spherical did not fit, and fitting spherical bearings in one end seems not that necessary, if you ask me.