Ther-Max 30â„¢ PVC Foam Ear Plugs from Tasco become continually softer while being rolled and after being inserted into the ear. This response to body heat produces an improved fit and far less pressure than conventional foam ear plugs. At 30 NRR, Ther-Max 30 provides the highest independently awarded NRR for a PVC foam plug.TASCO Corp., Providence, RI.