This is a brass Water butt tap with a polypropylene 3/4" male thread.
Usefull for replacing your plastic tap with a more sturdy and reliable brass tap.
It will screw directly into any 3/4" Female BSP thread which is the most common thread that you will find on a water butt.
A roll of PTFE Plumbers tape is included so that you can make the connection absolutely water tight.