The 20825 3700-4200 from Microwave Filter Company is a Waveguide Filter with Frequency 3.7 to 4.2 GHz, Insertion Loss 0.49 to 0.6 dB, Rejection 45 to 80 dB, Rejection Frequency 3.5 to 4.4 GHz. Tags: Band Pass. More details for 20825 3700-4200 can be seen below.