The WLJ4-400-600-40-4000-100 from Wainwright Instruments is a Low Pass RF Filter with Frequency DC to 400 / 600 MHz, Stopband Frequency Chosen Fco x 1.53 to 4 GHz, 3 dB Cutoff Frequency Choice of 400 to 600 MHz, Insertion Loss 0.3 to 0.35 dB, Rejection 40 dB. Tags: Module with Connector, Lumped Component Filter, Chebyshev Filter. More details for WLJ4-400-600-40-4000-100 can be seen below.