The BL-21 from MCLI is a 90 Degree Hybrid Coupler with Frequency 100 MHz to 1 GHz, Average Power 1 W, Insertion Loss 1.7 to 2.3 Db, Isolation 16 dB, Amplitude Balance ±1.2 to 1.8 dB. Tags: Module with Connectors, Octave Band. More details for BL-21 can be seen below.