... metal case 1,CE,SNR:27db,33db 2,smooth surface by anti-pollution treatment 3,wearing health,safety,rebound ... rebound, good flexibility, foam products even , uniform structure, smooth surface withoutadhesive, noise effective,SNR:33DB, This earplug can be washed ... directly affects the comfort level of wearing earplugs. 3.Surface textureSome earplugs feel sticky, they will stick the ear ...