Exact shaft dimensions 20.0 mm (0.780"); You buy .750 ID DOM; You will either need to ream the DOM or back off the shank .030". As this is a millimeter specification the listing should state that the connectors are 20.0mm and not 3/4 inch. 3/4 inch implies a tolerance of .750 and .780 just isn't enough. I don't mind pulling the shank back .030"; but I wouldn't buy if they were listed as 20mm.