Firm translucent plastic with a smooth surface and rubbery feel.
About this Product
This die is a shell surrounding a chunk of the support material, for cost purposes. It's 3cm in radius, which turns out to be a nice solid size for a die. The numbers look big enough to be readable, and it very decisively lands on a single face with a single face up. A handsome piece of random-number generation!
There's a 4cm version of this too, but I'm starting to think that might be overkill.