Form Foam Expands In The Ear Canal To Create A Comfortable Seal Against Noise And Provide An Optimal Protection Level. Plus, Since The Unique Foam Actually Softens And Becomes More Pliable With Body Temperature, The Seal And Comfort Increases The Longer The Plugs Are Worn. Ansi S3.19 1974/csa Z94.2., Nrr 28 Db Uom 200 Pr/box