This teal double dice d10 has a small while d10 inside of a larger translucent d10. With double dice you can roll a percentile with a single die -- because the double dice is actually two dice in one. The larger translucent d10 is substantially bigger than standard dice size, while the smaller interior die is smaller than standard. Double dice are an increasingly popular way of handling percentile rolls, though of course just rolling your percentile dice, or two d10s of different colors, works just as well.
Without question the double dice are an easier to roll and read solution than the d100, though perhaps not quite as cool.
Looks great, but I'd recommend using a felt tray for rolling this as I'm not sure how long the outer casing would last being rolled consistently on a harder surface. You're also going to want to put more wrist into this so it gets a good bounce. All in all, great deal.
My dice came quick. They were inexpensive, but not cheap.