A Mud Testing Kit is a field and laboratory set of instruments used to test the properties of drilling mud (bentonite slurry or drilling fluid) to ensure it performs properly during drilling operations (oil wells, boreholes, geotechnical works, etc.).
What it is used for
It helps engineers check whether the drilling mud can:
Carry cuttings out of the borehole
Maintain borehole stability
Control pressure
Cool and lubricate the drill bit.