The number of USB inputs located on the case of the card reader or hub (see "Type"). The number of USB ports that you will have at your disposal after connecting the device depends on this parameter. "Pure" card readers and combined models, usually, have 1,
2 and even
3 USB inputs, while hubs have
4 or more ports.
The length of the cable supplied with the device. Mostly relevant for models with a non-removable cable that cannot be replaced.
The main material used for the body of the device.
— Plastic. Plastic is light, cheap, quite practical, incl. has good strength properties. In addition, it allows you to create cases of complex shape and almost any color.
—
Metal. As a rule, aluminium-based alloys are used for metal cases. Such cases are much stronger than plastic ones, and also have a stylish appearance. On the other hand, in terms of impact protection, this material has no advantages over plastic, but it costs more, and it can weigh much more.