This is one of the first air (pressure gauge) integrated dive computers. In addition to being a basic dive computer, it calculates your remaining air time based on your consumption rate. This is not a NITROX computer. I do not have an owner's manual for this computer. I put a new battery in it and when it was pressurized, it came on. One cool feature it has is that if your tank pressure is low, the whole screen glows red. The battery, a Lithium 3.0 volt model 123A, will NOT be included.Due to eBay's new policy of charging the seller 9% of the SHIPPING FEES as part of the Final Value Fee, in addition to the 9% of the final sale amount, I am forced to raise my handling fees to at least $2.00 on each sale. The heavier the package, the higher the handling fee. This has already been included in the quoted shipping & handling fee listed with the auction. Sorry! If you win more than one item, I will combine them into one package, if it is practical, and reduce the shipping & handling fees accordingly. Please wait for my invoice. INTERNATIONAL SHOPPERS - eBay in the U.S.A. is requiring us to list a shipping service and cost for international destinations. Please use this information as an ESTIMATE of the shipping & handling cost. If you want an exact shipping quote, please e-mail me and I will be happy to send it to you. If you win this auction, please wait for my invoice before you pay.