Micro SD adapter won't work with iMac
I have two micro SD adapters, both of which work with a PC.
But when I used them with my new iMac, the computer doesn't recognise them.
Do I need a special one for the iMac?
iMac
The SD card specification for a memory card is 32 mm by 24 mm by 2.1 mm. You can also use thinner cards, such as MultiMediaCards (MMC). Cards that have a thickness greater than 2.1mm or that have surfaces that exceed 2.1mm should not be used. MiniSD, MicroSD, and higher density formats like MiniSDHC and MicroSDHC can also work with the use of "passive" adapters that conform to the width and thickness specifications listed above.
Example of a passive adapter:
copied verbatim from #2 and #3 in this Apple KB article: http://support.apple.com/kb/HT3553#3