The base material of the receptacle is typically nickel/ silver with the exception of the Size S-50C and Size S-50J which have a base material of beryllium copper.

There is a significant difference in resistance between beryllium copper and nickel/silver. In addition, beryllium copper is harder and stronger than the nickel/silver. It is for these reasons IDI manufactures the S-50J and S-50C Series receptacles from beryllium copper. All remaining receptacles do not require this strength and are made of nickel/silver. The ease of cold working and extruding makes nickel/silver a desirable, cost effective choice of material. In addition, nickel/silver has excellent resistance to corrosion.

Receptacles can be gold plated. The intrinsic properties of gold, resistance to corrosion and oxidation as well as its high thermal and electrical conductivity, make gold an ideal choice for this application. 

Gold will resist forming oxides, sulfides and other corrosion products and, since gold has a low resistivity, it has been an ideal choice for the electronics industry.

IDI receptacles are plated according to the following military specification: 
Gold—ASTM B-488-01