Ingersoll Rand 97166946 is an OEM hex nut used on the valve plates for the 7100 and 3000 T30 piston compressor pumps. The screw typically inserts from the bottom of the valve plate and secures the retainer plate, valves and dischage plate to the valve assembly. This nut then holds everything in place.
Typically 2-3 hex nuts are needed on each valve set depending on your pump model. This is for the hex but only and does not include the screw.