There are lots of different types of fire-based circus equipment. This is one of the more dangerous types :D
I was tasked with making these for my partner for a holiday in 2017. They worked great for all of 2 minutes and disintegrated so I decided to make a second set that means I would never have to make a third.
They are effectively cages for keeping the charcoal in. They are spun around at speed, like other poi, and the charcoal heats to a white-heat. Small bits of charcoal fly off and create some of the most impressive personal fire displays ever.
Version 2 is made from medical-grade stainless steel and used a lathe, a TIG welder and and angle grinder in the manufacture. Version 1 was made of cheap galvanised mild-steel wire and required only cutters and pliers. Long live the lathe!