The ‘core’ is metal, with plastic parts stuck onto it, and a decent bit of foam around the bottom to hold onto, which makes it comfortable and easy to use.
Fits my 5-band webbing straps just fine, and they are reasonably chunky.
The overall quality is reflected in the relatively low price for a specialist tool like this.
It does the job very well indeed - winds up straps as fast as you can turn the winder, so it’s quick! A real game changer compared to winding up straps with no mechanical aid. Has improved my truck-work life considerably, makes me smile every time I use it, but then I do like a gadget!