Used as a spare 1/4 to replace the 1/4 I lost from the complete set. I check the published sizes and am sure they fit perfectly in the place of the missing pieces. I even bought 2 in case I lose another one. I've used it and the screw it's used on actually has 8 pieces a piece and I sometimes make 8 or more pieces in a batch and they're tight so the tools have to stay tight. It fit perfectly the first time and after many uses it is still nice and snug. Very important.