This is a great product for keeping together various SIM cards knocking about at home. Each of the SIM card slot has a slightly raised track which can prevent the SIM card from sliding in smoothly if you are pressing down on the whole face of the SIM card as you slide it in. The trick is to press down on the end that is sticking out while you slide it in, this will raise the other end of the SIM card above the raised track so it causes no issues. I've probably made it sound tricky but it's easy once you try it for the first time. Although the width and length of the holder is credit card size, it is considerably thicker than a credit card and isn't very suitable for carrying around in a wallet or pockets (although this still possible if you do want to). Overall, it's a great product for the price.