Lot= 1 module (not pair)

SFP WDM 1.25G 20km DDM (DOM) SMF SC/LC 
(GLC-BX-D, GLC-BX-U),  Cisco compatible, NEW,
allow Reprogramming.

Initially, the modules have firmware compatible with Cisco.

You can reprogram these transceivers for operation in 100M or
You can reprogram these transceivers to achieve Hardware Compatibility other brands.
(Cisco, Intel, HP (HP Procurve), Juniper, Extreme, Brocade, Moxa, Alcatel, 3com, Nortel, AT, etc... )

Specifications:

Reach	20 km
Data rate	1.25Gb/s
Wavelength	1310nm/1550nm 1550nm/1310nm
Fiber/Cable Type	Single-Mode Fiber (SMF)
Connector	SC/LC Simplex Connector
Manufacturer	Third Party
Temperature	Commercial
Digital Output Monitoring (DOM, DDM)	Yes