Kingston KVR1333D3S9 / 4G RAM DDR3 1333 4GB SO CL9 KVR + (Personal Computers)
Very strange, works well on Mac mini 2.3GHz dual-core Intel Core i5 mid-2011 (2 slots only) BUT NOT more than 3 slots on my iMac 27 inch Processor Intel Core i7 quad-core 3.4 GHz mid-2011 ( refurbished). After installing my 4 modules, my 27-inch iMac