OWC 16GB UPGRADE: Consists of a single 16GB DDR4 2666 PC4-21300 CL19 2Rx8 288-pin 1.2V ECC Unbuffered DIMM Memory RAM Module Upgrade compatible with Synology NAS model SA3400D. 100% COMPLIANT: JEDEC-Standard and ROHS Compliant. Warranty-Safe Upgrade. Designed and Tested to Meet or Exceed all Manufacturer OEM Specs. EASY INSTALLATION: In Most Cases, Installing Memory is an Easy DIY project. Watch our OWC Basic Installation Video for Help. INDUSTRY LEADING: Consumer-friendly Advanced Replacement Program and Limited Lifetime Warranty, which includes Free Tech Support by Other World Computing. Replacement for Synology part numbers D4EC-2666-16G and D4EU01-16G.