One of a family of products manufactured by Custom Rubber Corp. for use in communication devices designed for hazardous environments. This particular part is a molded silicone rubber sealing cover that protects sensitive electronics capable of interpreting the vibrations in the back of your head when you speak. The device eliminates the need for a microphone inside an oxygen mask.
The material is a specially formulated silicone rubber that is pliable enough not to intefere with the electronics, but also durable enough to protect them from incedental contact.
BRP also worked with this customer to investigate and trial molding very soft gel-like rubbery material that had durometer lower than the Shore A scale can measure. Ultimately, the material did not work for their application but it showed some interesting characteristics.