Anyone that participates in the card collecting hobby for any amount of time learns something very quickly: You can never have too many sleeves on hand. No matter what your end goal with a card may be, a standard sleeve will almost always be helpful. Another thing collectors learn is that different thicknesses of cards need different sleeves. However, if you don’t know the thickness of your cards, the BCW Card Thickness Gauge shows several common thicknesses. Download and print Card Thickness Gauge (PDF).