HubBub adaptors go in the end of the handlebar and then they take the grip shifter..

most of the Gripshift is for 7/8" tube ,'mountain bike'.
some German companies get drop bars bent out of 22.2/7/8" tubes

then the above 3 piece kit works fine ,

German frame-builders do that to use Rohloff shifters in Road bikes ..

they dont fit on a 22.5 tube 22.22mm maybe certainly not on a 23mm bar ..


I have Trekking bars on my Rohloff hub bike ..