What is CASEIN?  It's a unique marbled material produced by acid precipitation of pure skimmed milk (which has varied applications as both a foodstuff and a plastic). Manufactured at only two locations in the world, Casein is powdered between steel rollers and laid flat.  Only 1mm per week can be laid down for the Casein to bond effectively.  A 10mm ear plug takes 4 months of preparation, followed by a further 3 months of hardening. The result is an inert/hypoallergenic plug.