The Model 660 is a premium hatch designed with a round base and cover and is intended for use in applications where tight sealing is critical such as sour crude/gas or where strict environmental emissions standards are enforced. The Model 660-L is a premium hatch designed with a long base and cover and is intended for use in applications where tight sealing is critical such as sour crude/gas or where strict environmental emissions standards are enforced. The long basin serves as a thief shelf. The Model 660-L also includes an inclining base to keep the basin level.