1. Mask with Gas-guide tube and a Canister with build-in transmitter for the convenience of talking when working. 2. Size of Canister: big, medium, small 3. Length of Gas-guide tube: 0.5m, 1m, 5m, 10m, 15m, 20m 4. Material of mask body:natural rubber 5. Can be equipped with different filters according to the environment.