THIS IS A SET OF THREE REPUBLIC THREAD RING GAUGES, ALL OF THE GO TYPE. THE SET INCLUDES A 2.375-8 N GAUGE WITH A PITCH DIAMETER (PD) OF 2.2938, A 2.632-8 NLH GAUGE WITH A PD OF 2.2808, AND A 2 1/4-4 NS GAUGE WITH A PD OF 2.0876. THESE ARE PRECISION TOOLS SUITABLE FOR MEASURING SCREW THREADS.