BILSOM THUNDER T1 Earmuff. The new Thunder series earmuffs offer top-of- the-line protection and comfort. The Thunder series feature patented Air Flow Control technology for optimal attenuation and a non-deforming headband that fits all head sizes. A ventilated inner-headband and soft ear cushions deliver maximum comfort. The easy-to-use Quick click height adjustment provides a snug and secure fit, and snap-in ear cushions are designed for easy replacement. The dielectric design is safe for electrical environments. Cap- mounted earmuffs include a set of adapters for use with popular hard hats. ANSI S3.19-1974/CSA Z94.2.NRR 26.