For all Luminox 8800 series watches (mine is the Recon)- use battery " 395 ". This is the Duracell type # commonly found at any drugstore. Other brand batteries are fine. Four screws on back of case that need a jewelers screwdriver - flat or phillips. Screws are stiff so be careful not to goof up screw heads. Once the back is off, be careful of any dust accumulation around the edge of both the back and case. Once any edge accumulation gunk is cleaned off, I removed the seal with my screwdriver, wiped it with a tissue, and spread a very thin layer of vaseline jelly on it, reinstalled the gasket, new battery, back and screws. Very fast, very easy.