Type i- Cards designed to the original specification (version 1.x) are type i and feature a 16-bit interface. They are 3.3 millimeters thick. Type-i pc card devices are typically used for memory devices such as ram, flash memory, otp, and sram cards.
Type ii - type-ii pc card devices feature a 16- or 32-bit interface. they are 5.0 millimeters thick. Type-ii cards introduced i/o support, allowing devices to attach an array of peripherals or to provide connectors/slots to interfaces for which the pc/laptop had no built-in support. For example, many modem, network and tv cards use this form factor.
Due to their thinness, most type ii interface cards feature miniature interface connectors on the card which are used together with a dongle; a short cable that adapts from the cards miniature connector to an external full-size connector. Type iii - type-iii pc card devices are 16- or 32-bit. these cards are 10.5 millimeters thick, allowing them to accommodate devices with components that would not fit type i nor type ii height. Examples are hard disk drive cards, and interface cards with full-size connectors that do not require dongles (as is commonly required with type ii interface cards).