Thomastik-Infeld Power-Brights Electric Guitar Strings, Heavy Bottom, Medium-Light .009 - .046 Thomastik-Infeld Power Brights Heavy Bottom Medium Light: More sustain and more basse with the Power Brights Heavy Bottom Medium Light. Round "Magnecore" winding (made of high carbon steel, then plated with nickel) around flexible hex core, brass-plated steel trebles, higher gain output at pickup resulting in better signal-to-noise ratio, great for use with effects or for long signal paths.