This document describes a 100G 1270nm to 1330nm 2km QSFP28 transceiver module. It includes specifications for the optical and electrical characteristics, as well as pin descriptions. Key features of the module include duplex LC receptacle optical interface, 4x25G electrical interface, transmitters using cooled 4x25Gb/s CWDM lasers, and receivers using 4x25Gb/s PIN photodetectors. It is compliant with standards including IEEE 802.3bm, QSFP28 MSA, and CWDM4 MSA.