1.strong destruction resistancy 2.service life is equal or greater than500 thousand 3.contact resistance is less than 100 ohm Main features: Highly antidestructive power Force 160-180 grams Contact resistance<100 Ω Service life≥ 500 thousand Main components: Zinc alloy chrome-plasted button Solid framework Electroconductive rubber PCB Metal bottom plate  Users choice: Button chrome-plasted colors: polished or sandblasted chrome Other usage keyboard is available besides using for telephone.