MFJ Enterprises Original MFJ-913 Balun 4:1 Current 300 Watts 300 Watt true current baluns/antenna center insulators that transforms 200 ohms to 50 ohms. Transmission Line Transformer construction using 100 ohm characteristic impedance transmission line gives flat 160-10 Meter response. Large low permeability ferrite cores easily handle full power. SO-239, stainless steel hardware with direct 14 gauge stranded copper wire connection to antenna. Heavy duty weather housing. Measures 4 x 2 inch diameter.