This Aerospace Information Report (AIR) includes general information about the various types and styles of flexible tanks and the tank-mounted fittings that adapt the tank to the surrounding structure and fluid-system plumbing. Recommendations are given relative to the dimensional layout of the tank when these recommendations serve to avoid tank fabrication problems and tank/structure interface problems. As a part of these recommendations, critical dimensions of plumbing adapter fittings are discussed and recommendations made. Tank manufacturing tolerances are given. Recommendations are made relative to cavity design and preparation to facilitate a reliable installation. The special installation requirements of non-self-sealing, self-sealing, and crash-resistant tanks are discussed. This document is not intended to replace the information or requirements of the military and commercial procurement specifications listed in section 3. No attempt has been made, except in a very general way, to include physical property data such as weight and thickness of the composite materials available in the industry. Such materials are too numerous and vary too much between manufacturers. Whenever specific data or advice is required, it is necessary that the tank manufacturers be consulted.