Crucial CT16G4XFD8266 16GB DDR4 2666 MT/S VLP ECC: Crucial ECC UDIMMs enable you to maximize the performance capability of your CPUs for a faster, more responsive system. Crucial VLP ECC UDIMMs measuring just 18.75mm tall, are 40% shorter than standard ECC UDIMMs and facilitate better airflow in space-constrained, systems such as microservers, routers, and switches. Crucial ECC UDIMMs contain error correction code (ECC). ECC parity helps detect and correct single-bit memory errors, which can cause sudden shutdowns, file corruption, or data loss.