Liquid Silicone Injection has made the process of customization much easier compared to Gum-Stock Silicone. Because liquid silicone is injected into two part molding system, customization is simple. Insert molding is achieved by having two molds, one mold to make the inserts such as colored keys, clear windows, or light pipes. Once the inserts are molded, they are placed into the keypad mold.
http://www.silimtec.com/basic-siloxane-polymer/
