For measuring the grease level in a holding tank, the grease trap sampler is designed for sampling liquid grease and oils. It will not work with solid or semi-hardened materials. The inside diameter measures 1-3/8", 3.5 cm allowing small food particles to easily pass through the valve opening during sample collection. The clear tubing is easy to see through and the 1 ft., 0.31 m red markers show the amount of grease accumulated in the tank. To use, slowly lower the sampler to the bottom of the tank - the valve opens and the liquid fills the tube. Lift the sampler up which closes the valve, holding the sample inside, showing the grease level. To empty, touch the plastic tip on a hard surface, and the liquid will flow out. The unit is made of two 4-ft., 1.22 m sections that screw together.