The 1-87133-1 is a Mod IV receptacle assembly from the AMPMODU Interconnection System, configured as a 12-position, dual-entry housing with both ends closed and designed for surface mount or vertical mount applications. The assembly features a .100 x .100 inch (2.54 x 2.54 mm) centerline spacing with .500 inch (12.70 mm) and .300 inch (7.62 mm) dimensions (A and B respectively), and is constructed from glass-filled thermoplastic housing rated 94V-0. Contacts are phosphor bronze with duplex gold and matte tin plating options, offering a voltage rating of 250 VAC, current rating of 3.0 amperes maximum per single contact, and dielectric withstanding voltage of 750 VAC. The assembly operates across a temperature range of -65°C to +125°C for receptacle assemblies and -65°C to +105°C for headers, with an insulation resistance of 5000 megaohms minimum and termination resistance of 12 milliohms maximum. Mating force is 9.0 oz (2.50 N) maximum per contact, with unmating force of 1.5 oz (0.42 N) minimum, and the contacts are tested to a minimum of 200 cycles for durability. These receptacle assemblies are commonly used in modular interconnection systems for telecommunications, industrial control, and consumer electronics applications where reliable, stackable connections are required.