The 0.125" (3.18mm) post length gives enough solder fillet for a reliable through-hole joint on boards up to 1/16" thick.
For a typical 18 AWG circuit in the MTA-156 system, the header can carry the full rated current of the wire without exceeding the 105°C upper limit of the thermoplastic housing.
Friction lock and vibration resistance
The friction lock on the top wall of the shroud engages with the mating receptacle's locking ramp. The single-wall shrouding protects the pins from bent-contact damage during blind mating. The glass-filled thermoplastic resists creep at elevated temperatures.
The base product number is 641210, which covers the full MTA-156 header family. No official pin-compatible replacement or cross-reference is listed — the 8-position right-angle gold-plated variant is the current production configuration.