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Flash Memory Card Buying Guide

Table of contents

What is a flash memory card?

Flash memory cards are extremely compact data storage devices made for use primarily in portable digital devices. With usably large data capacities and extreme levels of portability, flash memory cards can be used to store image data in digital cameras, data for handhelds/mobile phones, music files for digital music players, and saved game files for game consoles.

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Flash Memory Card Types

As mentioned above, there are many flash memory card formats. The most popular formats available today are:

  • SD (Secure Digital) cards
  • CF (Compact Flash) cards
  • Memory Stick
  • xD Card (xD-Picture Card).

Manufacturers also offer smaller versions of the above formats, such as Mini/Micro SD, RS-MMC and Memory Stick DUO for use in ultra slim digital products.

With so many different flash memory card formats available today, the key to choosing the proper format is to check and confirm the format(s) supported by your digital devices prior to purchase. For example, your digital camera may support only a CF card or SD card, therefore you should not purchase an xD card. If you are not sure about the format after checking the product, we recommended looking up the product user manual or manufacturer website, or to contact the retailer or manufacturer for assistance.


SD stands for Secure Digital. The stamp-sized SD card measures 24mm × 32mm × 2.1mm and weighs an inconceivable 2g. It is currently applied widely in a variety of digital devices, especially digital cameras and enjoys the largest slice of the flash memory card market. High capacity SD cards can even hold up to 32GB, but we can expect it to grow in the future.


Smaller and lighter than even the standard SD card, the MiniSD card is mainly designed for thin devices requiring smaller everything. Examples are mobile phones and digital music players. Measuring 20 × 21.5 × 1.4mm with an almost non-existent weight of about 1.4g, the MiniSD card is more or less just half the size of an SD card.

MicroSD (TransFlash)

Measuring just 11 x 15 x1mm, the MicroSD card is among the smallest of a new generation of flash cards. The MicroSD card is extremely useful in devices requiring much smaller flash memory cards, such as ultra slim mobile phones and other fashionably-designed digital devices.


MMC refers to Multimedia Card in full corresponding to the specs of MMCA (Multimedia Card Association). It comes with the dimensions of 24mm × 32mm × 1.4mm and weighs about 1.5g. Currently it has extensive applications in various digital devices.


As its full name Reduced Size Multimedia Card indicates, the RS-MMC features the same tech specs as the standard Multimedia Card but is built to smaller proportions. At dimensions of 24 x 18 x1.4mm and a weight of 1g it can be applied in smart phones, PDAs and toys.


This new Multimedia Card complies with MMC4.0 spec or above. It maintains the same size and shape as the standard MMC, but is capable of a much faster transfer speeds for better performance in comparison to the standard MMC.


MMCmobile is a new spec of RS-MMC and originally comes from MMC4.0 spec or above as well. It is of the same size and shape with the standard RS-MMC, but capable of a much faster transfer speed which allows it to perform much better than standard RS-MMC.


The Compact Flash Type I measures a relatively thick 42.8 × 36.4 × 3.3mm and weighs between 8g and 15g. CF I and SM cards (mentioned later) are both relatively early types of flash memory cards, and although most contemporary compact digital cameras only support SD/MMC cards, the CF card still enjoys the largest slice of action in the high-end digital camera market thanks to its massive storage capacities (currently topping out at 8GB).


The Compact Flash Type II card is 1.7mm thicker than the CF I card and weighs approximately 12g to 20g. With its extra thickness, the CF Type II card is capable of offering larger storage capacities of up to a whopping 12GB.


A Sony proprietary format, the Memory Stick is about the size of a piece of chewing gum and weighs 4g. It is rarely used now except in older Sony digital cameras and has generally been replaced with the Memory Stick PRO.

The Memory Stick can be widely used in recent Sony brand digital cameras and other compatible digital devices.


This next gen Sony Memory Stick PRO matches the original Memory Stick in terms of shape and size but is significantly different in terms of tech specs. While the Memory Stick has a maximum data transfer speed of 20Mbps, the Memory Stick PRO is capable of a much higher 160Mbps! Moreover, the MS PRO also represented a big breakthrough with respect to storage capacities – up to 4GB now from the Memory Stick's maximum of 128MB.


MS DUO refers to Memory Stick DUO which has the same tech specs with MS cards. With its dimensions of 20mm × 31 mm × 1.6 mm and weight of about 2g, MS DUO is almost of the half size of Memory Stick, so it is mainly intended for ultra small digital devices.

By attaching an adaptor, The MS Duo can also be used in products compatible with standard-size Memory Stick media.


The Memory Stick PRO DUO can be regarded as the embodiment of the MS PRO's tech specs (maximum data transfer rate of 160Mbps) and the MS DUO's physical attributes.

By attaching an adaptor, the MS Pro Duo can also be used in products compatible with Memory Stick PRO media.

MS Micro

MS Micro is short for Memory Stick Micro, also known as M2 for short. The tiny fingernail sized card is about 1/6th of the MS Duo's size.

An "M2" adaptor in the size of a standard Memory Stick will allow users to exchange data to Memory Stick PRO-compatible products.


The Smart Media is an older format that was introduced at about the same time as the Compact Flash card (mentioned above). Measuring 37 × 45 × 0.75mm, it is rarely used today and has been replaced in favor of the xD-Picture Card (mentioned below).


Developed by Fuji and Olympus, the xD-Picture Card broke the SM Car's 128MB storage limit and is capable of achieving 1GB at present with the potential to reach 8GB in future. The xD card is used primarily in Fuji and Olympus digital cameras.

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What else requires my attention?

As we mentioned at the top of this guide, the flash memory card format is a crucial consideration when finding and purchasing a suitable flash memory card for your electronic devices. In addition to this, there are other performance and usability features that require your attention as they directly influence how much data can be stored and certain performance aspects of the devices they are installed in. Let’s find out below.


The capacity of a flash memory card refers to the amount of data that it is capable of storing. A larger capacity, measured in MB (megabytes) or GB (gigabytes) will allow for more data (e.g. digital photos, digital music files) to be stored inside a flash memory card. Larger capacity cards generally cost more, so it maybe advisable to purchase a card that meets your requirements rather than one that is on the cutting edge in terms of storage limits. Please see our Flash Memory Capacity Guide for more details.


The speed of the flash memory card has a crucial influence on certain aspects of a digital device's performance as higher transfer speeds mean that data can be read from or written to the card at a quicker rate. A high resolution image shot at high quality settings will typically result in a large image file that requires time to store to the flash memory card. A higher speed memory card reduces the amount of time needed for this operation and is crucially important when the camera is operating in burst/continuous mode, where it needs to transfer image data from its buffer to the flash memory card as quickly as it can to make room for more shots.

Like optical drives, most flash memory cards use the X rating for speed. Others may simply be marketed as "High Speed" cards instead. A speed of 1X corresponds to 150KB/s, i.e. 150 kilobytes per second, and therefore a speed rating of 20X should in theory correspond to a speed of 3000KB/s (3MB/s).

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Other useful accessories

Card Reader

While data can be transferred between the flash memory card and your computer by connecting the digital device (e.g. digital camera) directly to your computer via USB cable, some degree of extra convenience can be had with the help of a card reader that will directly accept the camera's flash memory card.

Most card readers today are capable of supporting almost all types of flash memory card, although some are compatible with only one or two types. USB card readers are compatible with most computers equipped with at least one USB 1.1 or USB 2.0 interface, while PCMCIA card readers are intended for use in notebook computers.

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