This is a spare toilet tank for the Eco-Safe Portable Toilet System. Tank size is 5.5 gal and measures 17.0″ x 7.5″ x 13.5″ tall. All tank corners are well rounded for easy cleaning. The entire system meets BLM, NPS, and USFS requirements for washable and reusable toilet systems. This tank accomadates 50 user waste days.