Love the square drive.  This, to me, is among the most positive locking drive forms right next to star drive.  I HAVE had a few that fit a little looser on the drive than others.  Might be a worn die at the factory?  In any case, these work GREAT 99% of the time for me.  I've gone thru a LOT of Kreg screws and these work great.  I created my own assortment of each thread style & length.  These are used for bonding softwoods to softwoods.