Secure Digital (an SD Card) is a highly secure stamp-sized digital camera memory card. Jointly developed by Matsushita Electronic, SanDisk and Toshiba, an SD Card weighs approximately two grams. The SD Memory Card, measuring 24mm by 32mm by 2.1mm. SD Cards can be used in a variety of digital products; digital music players, cellular phones, handheld PCs, digital cameras, digital video camcorders, smart phones, car navigation systems and electronic books

The mini SD card was developed to meet industry demands for downsizing mobile phones. It is only 37% the volume of an SD Memory Card.  The mini SD Card, measuring 20mm by 21.5mm by 1.4mm. Some mini SD cards include an adapter that converts the mini SD card into a full size SD card to be used with the growing number of SD compatible devices available in the market.

The micro SD card (also known as TransFlash card) is a type of removable flash memory card designed specifically for mobile phones and other small devices. The micro SD Card, measuring 15mm x 11mm x 1mm. It is getting more popular and popular because its size and the popularity of slim designed mobile phones and the tiny MP4 video players.