Freeman oval hinged hatches have a unique hinging device that allows the hatch to be opened more than 180 and floats when the hatch is closed to facilitate a tighter seal. Round hatches 18" and larger, and all oval and square hatches with aluminum covers are available hinged from the factory 15" x 24" clear opening dimension is a standard used by many throughout the world as a crawl-through access opening Rectangular 18" x 24" clear opening hinged hatch is intended for weld-in applications Sizes reflect size of opening Hatch cover is constructed of cast aluminum