To maintain the stated sound attenuation performance of your earmuffs, it is important to regularly replace cushions and inserts. Under “normal use”, you should replace the hygiene kit at least twice per year. For proper performance, always use genuine Sordin replacement parts. These kit is for the SFA (Sordin Flexible Attenation) 32dB versions with extra thick inserts. Sordin Supreme SFA Hygiene GEL Kit 60183-S