X2 & XENPAK Transceivers are different from each other in form factor only. X2 is a bit smaller form factor than the XENPAK. Because of their bulky structure, X2 & XENPAK Transceivers are now being replaced with SFP and SFP+ transceivers, very few of the Cisco switch series make use of X2 & XENPAK Transceivers. Both the X2 & XENPAK Transceivers have SC connectors, exception being X2-CX4 that uses InfiniBand connectors. Another point of difference among X2 & XENPAK Transceivers is that LRM specification is available in X2 format only. On the other hand, LX4 (characterized by 4 x 2.5 Gb wavelengths) is available in both X2 & XENPACK Transceivers. X2 & XENPACK Transceivers modules are connectible with each other as their optics are of same transceiver type.