PM606E-DG Brass Outage (Ullage) Plumb Bob with Deep Grooves
Solid Brass 7/8" square X 6" long with Phenolic black plastic case.
Graduated to 16ths, reading left to right, with inch markings from top to bottom.
Deep groves long side of scale for accurate indications using product finding pastes.
Designed to accurately measure the distance from a fixed reference point on top of a tank to the surface of the liquid inside the tank. The zero calibration point is at the inside top of the bob hole. They have grooves on the brass side adjacent to the PHENOLIC scale as recommended by API.