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 Rackstation models RS3621RPxs And RS3621xs+. 100% COMPLIANT: JEDEC-Standard and ROHS Compliant. Warranty-Safe Upgrade. Designed and Tested to Meet or Exceed all Manufacturer OEM Specs. INCREASED PERFORMANCE: Memory Upgrades are the Most Effective and Easy Way to Boost your PC's Performance. INDUSTRY LEADING: Consumer-friendly Advanced Replacement Program and Limited Lifetime Warranty, which includes Free Tech Support by Other World Computing. EASY INSTALLATION: In Most Cases, Installing Memory is an Easy DIY project. Watch our OWC Basic Installation Video for Help.