Compatibile Model Information iMac A2115 Class: DDR4. Ram Class: DDR4. SubFamily: 2019 / 5K. Capacity: 16GB. Apple iMac PRO models require the use of ECC RDIMM modules. Kit Capacity: 16GB. Your computer loads a program or file you select from the hard drive in to your computers RAM, then it will access each bit of data from there.