Game card sleeves often come in different sizes to accommodate different types of game cards. Different games may use different sized cards, so the card sleeves will be sized accordingly.

Here are some common game card sleeve sizes:
 

Standard Size: The most common game card holder size is standard size, which is suitable for most regular card games, such as poker and most trading card games (TCG) or card games (CCG). Standard size game card holders are usually 63.5 mm x 88 mm (2.5 inches x 3.5 inches).
Small Size: Some card games may use smaller cards and require card sleeves of corresponding sizes. For example, some Japanese trading card games (such as "Yu-Gi-Oh") often use small-sized cards, and the corresponding card sleeve dimensions are approximately 62 mm x 89 mm.
Large Size: Some games may use larger size cards and require specially designed card sleeves to protect these large size cards. The size of large card sleeves will vary from game to game, such as special skill cards in some role-playing games (RPGs) or large game cards in board games.
Additionally, there are some custom-sized card sleeves designed for specific games or specific card types to ensure optimal fit and protection. When purchasing a game card holder, make sure to choose one that matches the size of the cards you own to ensure optimal protection and usage.