Small animals tend to live shorter lives than larger animals. There are a few theories as to why that is, but the one I believe is most popular is: small animals tend to live shorter lives anyway (because of threats from predators), so there are fewer opportunities to evolve to be long-lived.
The American National Standards Institute (ANSI) Class 150 is a system of dimensional standards for weld neck, threaded, slip-on, lap joint, socket weld and blind flanges. Dimensions for facing, bolts and studs are also included in ANSI Class 150. ANSI Class 150 establishes measures for pipe sizes.
Lap Joint Flanges: A Lap Joint Flange is a two piece device that is much like a weld-neck flange but also like a loose slip-on flange. One piece is a sleeve called a 'Stub-end and is shaped like a short piece of pipe with a weld bevel on one end and a narrow shoulder on the other end called the hub.