The Aluball is a strainer used to prepare various drinks. It was designed for kava, but it can also be used to make coffee or tea. It is basically the same concept as a tea ball, but with a finer mesh, since kava solids can be gritty and unpalatable.
The Aluball is made of plastic with very fine (75 micron) steel mesh nets that allow kavalactones to diffuse, but keep out the grittier kava solids. A user will place a table spoon of kava powder in the aluball, place it in a sealed container with warm water, and after about 30-60 seconds of vigorous shaking, have a relatively-palatable (and hopefully potent) kava drink ready to go.
As a final note, although the name might suggest this is made of aluminium, it is not: according to the website, it is derived from the Tongan verb “Alu”, meaning “to go”.