The 51-304B-dBF-dBR-6-6-6-6 from Narda-ATM is a Waveguide Coupler with Frequency 15 to 22 GHz, Coupling 3 dB, 6 dB, 10 dB, 20 dB, 30 dB, Directivity 40 dB. Tags: Multihole Coupler, Broadwall Coupler. More details for 51-304B-dBF-dBR-6-6-6-6 can be seen below.