The 21000 3800-4200 from Microwave Filter Company is a Waveguide Filter with Frequency 3.8 to 4.2 GHz, Insertion Loss 0.37 to 0.65 dB, Rejection 45 to 75 dB, Rejection Frequency 3.64 to 4.325 GHz. Tags: Band Pass. More details for 21000 3800-4200 can be seen below.