Soft memory foam helps isolate noise while staying comfortable and in place. When used on our Custom Molded Earplugs the foam tips will give you the highest Noise Reduction with an NRR of up to 31. Foam tips will wear out with general use we recommend replacing foam tips every 4-6 months. The Small foam tips are the standard size included with the Custom Molded Earplugs. When used with our Earphones these foam tips will give you better noise isolation and help bring out the clear bass and crystal highs for an even better premium sound quality.