SanDisk's TransFlash memory card format has been adopted by the SD Card Association as microSD.

The card, which is already used in some mobile telephones, is similar in appearance to a cell phone SIM card. It measures 15mm by 11mm by 1mm, which makes its volume about 165 square millimetres. That's three and a half times smaller than miniSD, which until now was the smallest SD format card, and about one-tenth the volume of the SD card.

TransFlash can be used in SD card slots with the use of an adapter.

SanDisk has promoted TransFlash to date as a memory expansion format for mobile phones. Because of its small size, it's better suited to mobile handsets than are larger cards, the company said. TransFlash slots can already be found in phones from Motorola, LG Electronics, Samsung, Kyocera and Sagem Communication.

To coincide with the format's adoption by the SD Card Association, SanDisk said Wednesday it is now shipping a 256MB capacity microSD card and will be followed in August by a 512MB card, SanDisk said.

SanDisk also said it plans to launch a 1GB card this year and a 2GB card next year.