The D21-A1 from ANOISON Electronics LLC is a DC Block with Frequency 30 MHz to 26.5 GHz, Insertion Loss 0.80 dB, Breakdown Voltage 50 V, VSWR 1.20:1, 1.25:1, Operating Temperature -55 to 125 Degree C. Tags: Inner DC Block. More details for D21-A1 can be seen below.