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 - YELLOW Cornelius type Pressure Relief Valve (RPV) (17psi/1.2BAR)
KL05333 - RED Cornelius type Pressure Relief Valve (RPV) (35psi/2.5BAR)
KL09164 - GREEN Cornelius type Pressure Relief Valve (RPV) (65psi/4.5BAR)
KL03070 - GREY Cornelius type Pressure Relief Valve (RPV) (100psi/6.9BAR)

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