Noah Tucker They can of course be used as d10s. Or you can colour the two sets differently (so that Blue 5 is actually 15 and Blue 0 is actually 20, whereas Red 0 is really 10 and Red 5 is… Standing by?), to create a d20 that is marginally more balanced than a regular one (two digits = more material carved away on half of the sides). Also rolling two of these they’re easier to use as d100s than regular d20s.