Hex plug gauge 4.75 MM A/F, Hex. Plug Reversible double sided GO Gauge -4.752 to 4.757 A/F - GO Depth 2.040 to 2.045, Nogo Depth 2.273 to 2.286 mm (Required to Check The HEX Slot For 4.5 & 5.0 mm Atlas HFN  Screw HPG4752.4826.2040.2286)