[2] Improvements included a single combined seat and parachute quick release fastener (QRF) and a snubber mechanism to allow crews to lean forward without loosening the harness.

[2] The first successful ejection using a Mk.4 seat took place in March 1957, the aircraft involved being a Fiat G.91.

As the seat moves up its guide rails an emergency oxygen supply is activated and personal equipment tubing and communication leads are automatically disconnected, leg restraints also operate.

A barostatic mechanism prevents the main parachute from opening above an altitude of 10,000 ft (3,000 m) allowing the seat and pilot to descend rapidly in free fall so conserving the on-seat oxygen supply until normally-breathable atmospheric air becomes available.

[2] The Mk.4 ejection seat has been installed in over 35 aircraft types including the following: List from Martin-Baker.