These are module with different ranges:
Cisco X2-10GB-CX4
The Cisco 10GBASE-CX4 Module supports link lengths of up to 15 m on CX4 cable.
Cisco X2-10GB-LX4
The Cisco 10GBASE-LX4 Module supports link lengths of 300 m on standard Fiber Distributed Data Interface (FDDI) grade multimode fiber (MMF).
Cisco X2-10GB-SR
The Cisco 10GBASE-SR Module supports a link length of 26 m on standard FDDI grade MMF. Using 2000 MHz*km MMF (OM3), up to 300 m link lengths are possible.
Cisco X2-10GB-LR
The Cisco 10GBASE-LR module supports a link length of 10 kilometers on standard single-mode fiber (SMF, G.652).
Cisco X2-10GB-ER
The Cisco 10GBASE-ER Module supports a link length of up to 40 kilometers on standard single-mode fiber (SMF, G.652).
