3X Longer Life - Incredible Tone - Gentle Feel - High Output - Rich Sustain Freeze strings to -320ºF to tighten molecules and minimize fine gaps. This process eliminates transient frequencies that are rough and turbidized treble and bass, resulting in a more stable, true tone and longer life string. With 8% nickel-plated steel outer circumference on a tinned mandolin wire hex core, the blue steel string has been a best selling item in the world for over 30 years and is loved by the best musicians around the world. Once you try the blue steel string, you will be able to match the charm. It has a harmony that cannot be achieved by other strings, providing superior feel, precise pitch and durability. Our dream is to make strings to make your dreams come true.