Every module in this series is a 240 pin DIMM unit, which is about double the size of a SODIMM unit. Four of the five models in this series come in two pieces, the Q2X8G6400C4DHX being the one exception with a four-piece kit. The five models that make up the XMS2 DHX series are all very similar, the only differences between them being their GB size (2GB-8GB), Tested Latency (TL), and voltage.