The bore hole size of the handles is incorrect and to fit these handles to the original shafts required the use of a reamer the exact size to allow the handles to fit. Quality control and measurement are the issue here of the production of the handles whereever they are made and if i did not own an extensive array of machine reamers i would not have been able to assemble the vent windows and complete the job. Downtime approx. 1 hr. for the process of reaming the holes out to the same size as the original 40+ yr old handles. Not happy.