I love Calvin Cuboids! The I cube is a lot of fun and it actually is a very fun challenge. It looks like a regular cuboid though when you turn the center M it sticks way up in the air; kind of like a mirror block puzzle. It is awesome to solve and if you like cuboids, you will love this cube. Specs: nice quality plastic, great concept with the elevated M. design, great if you are a collector of cuboids, nice sticker quality, a fun challenge. I would recommend this puzzle for sure. ,