There isn't a Nifty MiniDrive designed specifically for (and thus guaranteed to work with) any of the iMac models. However, you can check if one of the models (one for MBA, MBP, or rMBP) might work with your machine. To do this, insert a standard SD card and mark how deep it goes in and select the Nifty MiniDrive model that has the same or slightly greater length. Those are: 21.5mm for MBA 21.2mm for MBP 15.8mm for rMBP