Here we have a single opaque red jumbo D20 with white numbers by Koplow, the NICE DICE(R) Company. This RPG die measures roughly 30mm in size (measured while sitting flat on table).

Please note that the pattern on this die is not one perfectly solid color. The process used to make jumbo dice creates a streaking pattern which can be visible on the surface of the dice (to see an example of this, click here). This will only matter if you need a perfectly solid color. Other than that, the streaking is actually an interesting effect that adds some variation to the otherwise plain color.