Memory for iMac12.1 (mid-2011)
I always suggest that people check with the company called Other Word Computing, at macsales.com. They specialize in Macintosh memory upgrades and they provide good technical support. If you know the exact version number of your Macintosh, they can tell you exactly what the upgrade possibilities are and give you the exact memory specifications for your particular model. They post notices about which Apple firmware updates must be applied to your specific model before you attempt an upgrade. Of course they sell RAM at good prices, but you could use their upgrade advice to purchase RAM of the appropriate specification from a different company than theirs.