3M 1100 Earplugs equipped with a probe tube for fit testing using the 3M E-A-Rfit™ Validation System. Cannot be used for hearing protection. 3M™ 1100 Probed Test Plugs are a specially probed version of the standard plug. This product works with the E-A-Rfit Validation System and allows you to conduct an earplug fit test for the 1100 and 1110 earplugs.