The better version of a ball tea strainer.
Very easy to fill with a dedicated tea measuring spoon, one spoon is the perfect amount.
Almost no tea is lost while brewing, just remember to make sure no tea is left on the edge. It needs a tight fit.
The hook fits over the edge of a straight tea glas. Just open the hook a little. It needs a counterweight for regular tea cups as far I can tell.

Perfect little gadget for making a cup of tea.