The 3M Speedglas 9100FX/ 9100 FX-Air extended coverage for the crown portion of the headgear is for use with 9100FX/ 9100 FX-Air welding helmet assemblies to help protect user from welding spark and spatter on the top portion of the head and neck.
3M Speedglas Welding Helmet Extended Headcover 9100 FX/ 9100 FX-Air, Welding Safety 06-0700-82 Review