These are part of the Chessex Lab Dice and come with a commemorative Lab Dice D6 Pip.
Lab Dice are test dice (and only available for a limited time) and allow Chessex to release a lot of colors into the market, using public reaction to gauge which colors are the best to be integrated into their normal dice ranges. Only some sets from previous lab runs have made it into main stream production, and most have been changed, making these limited editions.
