The MFJ-913 is a 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 4¼ x 2 inch diameter.