The trigger from CZ UB, I haven't seen it. But since I do have a TS, and that is for a TS, I would assume that it does not have the opening on the top to allow the trigger spring to rest on the frame. That notch would have to be made by cutting filing. I would prefer the CZ custom route, with the trs, trigger and the pin combo. A couple of pins and springs,in fact. That's what I did! Flat trigger, if set right, looks excellent I have to admit.