Double d20, clear and red

'A small red d20 in a large clear d20. For D&D 3.5, use this If you want to know if a Critical Threat is also a Critical hit right away. For D&D 5e, you can use this to roll advantage/disadvantage in one roll.
Note: The outer die is a spindown. Spindown dice are numbered sequentially, so they can be used more easily to keep track of points.