The BLK from Shanghai Huaxiang Computer Communication Engineering is a DC Block with Frequency 10 MHz to 6 GHz, Insertion Loss 0.2 to 0.5 dB, Breakdown Voltage 72 V (DC Voltage), VSWR 1.20:1, 1.40:1, Operating Temperature -55 to 100 Degree C. Tags: Connectorized. More details for BLK can be seen below.