It can be used by beginners and advanced users to lives from drowning caused by waves, falling down due to loss of scaffolding, etc. It can be used easily by beginners and advanced users. It automatically inflates in 3 seconds when it comes into with water, and it can al be inflated by manually pulling the rope. It can be used normally from -30 degrees Celsius in the middle of winter to the hot weather in midsummer, and it can be easily worn in winter with a thick coat. The D-type part is mainly very useful for connecting the rope thrown by the r and pulling it onto land in the of a maritime accident. There is a whistle next to the air intake pipe. In of drowning, al blow the mouthpiece to call for help from people around you. In addition, a reflective band is designed that it can be seen in the dark and can be easily found by rs.