These are the widely used positive displacement type flowmeters. They consist of a moveable disk which is positioned on a concentric sphere situated inside a spherical side-walled unit. Universally, they are employed as residential water meters.
They exist in various sizes and capacities and can be constructed from a wide range of materials. Their typical size range varies from 5/8-in to 2-in sizes. They are ideal for pressure ranges around 150-psig with an upper limit of 300 psig.