What are Type I, Type II and Type III PC cards?

A. Type I, Type II, and Type III PC cards are portable storage devices, each about the size of a credit card. The main difference between each type of card is their thickness. Type III PC cards are thicker than Type II PC cards, and Type II PC cards are thicker than Type I PC cards. Type III PC cards are thicker to accommodate more electronics than say a Type I PC card. The most prominent Type III PC cards are hard drives; however, Type II PC card hard drives have become available in recent years. Type I PC cards are less common because they're primarily available as Flash storage cards and tend to be more expensive than other types of storage cards such as CompactFlash (CF).