This is a safety device for KL06972 Mini Keg Tapping Head Kits. It has a 1/4" BSP threaded bottom to Cornelius Pressure Relief Valve thread type on top.

This piece can be used in conjunction with:
KL22569 -
KL05333 -
KL09164 -
KL03070 -

Please note the pressure rating of the device you are pressurising. Failure to do so may cause serious injury