8GB (two 4GB SO-DIMMs) of 2666MHz DDR4 memory Brand new unused memory. MemTest passed 100%. Apple certified, high quality. Compatible with the newest notebook PCs and Apple iMacs supporting 2666MHz RAM. Please contact me if you have compatibility questions. Fast same day ship. About FastMacs: A global supplier of full-duty production level systems for creative professionals, we are a group of electrical engineers who specialize in testing, improving and upgrading Macs beyond what's available from Apple. With over 30 years of combined Apple experience, our team custom configure Mac workstations for media professionals, artists, audio engineers, scientific community and power users. If this is not the ideal configuration for you, our expert team can assist. Tell us your application and specification. Our team can design one and list it just for you. Purchase with confidence: - We have over 24 years of experience and awarded with Top Seller status. - Perfect 100% feedback rating selling our top of the line Macs to demanding professionals. - We stand behind all of our products we sell, period. - We have a firm belief in building lasting relationships with our customers not just making a sale. Your satisfaction is guaranteed. If you are not completely satisfied, We will not hesitate to refund you. Feel free to contact us for any questions. We?re always ready to assist. *** Want us to install this upgrade? *** Our expert upgrade team can help. Please contact us and we'll be happy to discuss the possibilities and provide you a quote. See our other items! Like what you see? Be sure to follow us.