OWC 8.0GB UPGRADE: Consists of an 8GB PC19200 DDR4 2400MHz SO-DIMM Memory, 260-Pin, 1.2 Volts, Non-registered, Non-ECC, Fully compliant with JEDEC specifications, ROHS compliant, warranty safe upgrade; Backed by OWC Memory Lifetime Limited Warranty including the OWC Lifetime Advanced Replacement Program. COMPATIBLE WITH: 2017 iMac: iMac w/Retina 5K display (27 inch mid 2017) Model ID: iMac18,3 (3.4GHz & 3.5GHz & 3.8GHz Core i5 & 4.2GHz Core i7). COMPATIBLE WITH: 2017 iMac 21.5-inch: Model ID: iMac18,2 iMac w/Retina 4K display, 21.5-inch Mid 2017, (3.0GHz & 3.4GHz Core i5 & 3.6GHz Core i7); Model ID: iMac18,1 iMac Mid 2017 2.3GHz Core i5. COMPATIBLE WITH: PC Laptop, PC Notebook, & All in One Computers. INCREASED PERFORMANCE: Memory Upgrades are the Most Effective and Easy Way to Boost the Performance in Your Mac Pro. COMPATIBLE PART NUMBERS: CT8G4S24AM, CT2K8G4S24AM, KVR24S17S8/8, CT8G4SFS824A, CT2K8G4SFS824A, KCP424SS8/8, HMA81GS6AFR8N-UH, M471A1K43BB1-CRC, M471A1K43CB1-CRC, M474A1G43DB1‐CRC, HMA81GS6AFR8N‐UH. INDUSTRY LEADING: Consumer Friendly Advanced Replacement Program and Limited Lifetime Warranty, which Includes Free Tech Support by Other World Computing