Official battery replacement for the Cressi watch-style dive computers only, Models: Cartesio, Goa, Neon, King, Nepto. The kit is composed of the O-ring and the pair of little screws with nylon washer for the battery cap. The battery is excluded. It is recommended to proceed carefully with changing the battery and the O-ring. In case of trouble, it is suggested to contact an authorized service center to change the battery. The Cressi Authorized Dealers are listed on the official Cressi website.