The 3M™ Speedglas™ Headband Back Part 9100 is a replaceable spare part replacing only the back portion of the headband if the original parts become worn or damaged during use.3M Speedglas Welding Helmets 9100 Series feature optimal respiratory protection and comfort for increased productivity and demanding environments. The radical technology behind the highly adjustable head suspension fundamentally changes not only how you wear the helmet, but also how you experience fit, stability and balance. 3M Speedglas Series Welding Helmets 9100 have a smooth up and down pivot action that gently locks in the up position, and the suspension keeps the helmet closer to users head making the helmet feel lighter, more stable and balanced at all times. The 3M Speedglas Series Welding Helmets 9100 are also available with shade 5 SideWindows, allowing you to see others working around you.