AddOn - DDR4 - 4 GB - SO-DIMM 260-pin - 2133 MHz / PC4-17000 - CL15 - 1.2 V - unbuffered - non-ECC - for EliteBook 820 G3, 820 G4, 840 G3; ProBook 440 G4, 470 G4, 470 G5; ZBook 15u G3 (non-ECC), Studio G3 (non-ECC).