packaging sleeves are really great for protecting cards, but I'm sure a lot of players and parents have thought of the fact that cards for different games are different sizes. It is important to be able to distinguish these sizes or you could end up buying something that doesn't fit your cards, which can be a big disappointment. This can be a bigger problem than you think because there are two common card sizes, and when looking at the sleeves they can look almost identical. WIthout paying attention you could pull the wrong size right off the shelf without even noticing.
First, Magic: the Gathering and the World of Warcraft Trading Card Games use a standard card size. I consider this standard because they are about the size of a playing card, and playing cards have been around for a much longer time than any of these games. These sleeves will fit other cards too, in fact the vast majority of cards are made with the standard size. Specifically this size is 66mm x 91mm. This can often be found on the sleeve package or in the item description online. It is important that you look for this because the non-standard size is smaller, and those sleeves will not fit on a card from Magic or WoW trading card games. A lot of the sleeves will specifically mention the card game that the sleeves are for, so make sure to look for that also.
The second size is for the Yu-Gi-Oh card game. These cards are smaller and as such the sleeves are also smaller. I am not sure why it was decided to make the cards smaller, but since Yu-Gi-Oh is such a popular game this has become a significant problem. There are nearly as many Yu-Gi-Oh sleeves on the market as there are standard sleeves, simply because Yu-Gi-Oh is such a popular game and because the younger Yu-Gi-Oh players seem to enjoy using sleeves with cool artwork. The sleeve size is 62mm x 89mm, and usually on the package Yu-Gi-Oh is specifically referenced, since they are the only card game that uses this size that I'm aware of. Most hobby shops that carry card games will have two separate sections for these sleeves, make sure you are in the right category for your game.
