The 1:1 Current Balun was designed to replace the center insulator of a dipole antenna.Outstanding low permeability ferrite mix coated toroid core with special design for maximum bandwidth by KB2 Product. Operates 3 to 54 MHz. The KB2 Current Balun will reduce or eliminate stray RF often found on coax. This stray RF can cause burns and other problems with electronic equipment in ham-shacks and vehicles. Stray RF also results in a loss of radiated power from the antenna, which will lead to a great reduction in signal strength. There are waterproof gaskets, suitable for outdoor long-term use, but can not soak into the water. Made in China.If you need to the mass orders, please contact customer service. Thank you. 4:1 baluns are designed for 50 ohm unbalanced (coax) input to 200 ohm output (either balanced or with one side grounded).