We have become dependent on our dive computers to the point many divers don't even own a set of dive tables anymore. This is not a good trait to have as a safe diver. These dive tables are based on where it all started The U. S. Navy. Make sure you have a set in your Save-A-Dive Kit just in case you're your computer craps out. Water proof dive tables easy to follow flow chart, has U.S. Navy decompression tables to 190 ft. 6" X 8"