The 4 key holder doesn’t hold cards, just the 6 does. I use mine for my keys, and I fit a driver’s license and debit card in the back. Occasionally I’ve fit a few bills of cash. You can’t fit a ton o cards, so if you really need something that will hold many cards you should go with a cles. However, just a gym card and and license, then you should be great with the 6 key holder. I personally love it more than the look of a cles, which is why I use it!