The Pee Wee is approx 0.5" or 12mm and is just a wee bigger than the Itty Bitty. The Pee Wee marble kit has 15 marbles, including cats-eyes, black speckled, translucent red, royal blue, clear, black with yellow or red. An opaque red, white and blue, and a red with yellow. Buy some Pee Wee semi-precious gemstones or "gem marbles" to add even more variety to your options! Sold separately.