HPS428 premium cap mounted ear muff is designed to mount on to most brands of slotted hard hats. The cup pads are soft and comfortable which are ideal for extended use. It comes with strong, stainless steel wire swivel fork arms to ensure strength and durability with easily adjustability for quick and convenient positioning. The HPS428 has one of the highest NRR ratings for a cap mounted muff (28 dB) ANSI S3.19 which was independently tested and certified with a CSA Class A.