The FerMonster Plastic Carboy fermenters are made from PET plastic (same as 2L soda bottles) which is far more resistant to oxygen than regular plastic. Plastic PET carboys are safer than glass carboy fermenters. Full carboys can be heavy and hard to maneuver and glass can break resulting in possible injury. Also with a wider 4" mouth, there is easier access for cleaning. Specifications: Uses a #10 stopper Comes with an O-ring and an air tight lid with a hole for the #10 stopper (Solid lid also available but sold separately)Weighs 1.5 lbs Rated to 140 degrees : 20.9 inches Diameter: 11.3inchesCompletely taste and odor free.