This "6 sided" die actually has 14 sides, 8 of which are triangular, making it a cuboctahedron. It has 6 square sides which oppose and are marked like a 6 sided die. It rolls very nicely due to its hollow design and can be seen through if held at the right angle. It's also pretty small (12mm cuboid).
It can be rolled in any situation that calls for a standard die but please note that it sometimes lands with a triangular face up and thus might need to be re-rolled to roll a number. It's quite fun to treat the blank triangular faces as "0" and experiment with how that changes some of your favorite board games.
Let me know in the comments if you'd be interested in a D14 version, i.e marked with numbers 1-14.