That format (3.5" or 5.25" ) don't matter, you want to pay attention on the connector, is it USB2.0 or USB3.0? because usb3.0 is faster than the USB2.0, but you may pay more $$ for it. Here is one review ( old one) http://www.pugetsystems.com/labs/articles/Card-Reader-Comparison-USB-2-0-vs-USB-3-0-126/