Southco Tubular head styles are used to add a level of security for E3 compression latches compared to the normal tool access type of recess. Tubular Key heads can be identified by a deep circular recess in the face of the latch similar to the image shown.
Small E3 latches have a head diameter of 21.0 millimeters and a body which is 13.0 millimeters across flats.
Steel key with Nickel plating