Materials:

Body: diecast zinc alloy with tarnish resistant nickel plating.
Mounting bushing: nickel-plated copper alloy.
Insulation: Rigid plastic.
Springs: Copper alloy.
Sleeve terminal: Copper alloy.
Hardware includes: One copper alloy nickel-plated hex nut
One steel nickel-plated washer.
 

Specifications:

Number of conductors 2 (7146), 3 (7157)
Contact resistance < 0.05 Ohms
Dielectric strength 500 V dc
Insulation resistance 1000 MOhms
Maximum panel thickness: .25 inch (6.35 mm) for .375 inch (9.5 mm) long bushing.
Model 7156: 2-Conductor (mono), .205" Faston terminals and .375" (9.5 mm) long bushing.