The Matco Tools Battery/Coolant/DEF Refractometer, No. MST401, allows users to check the coolant and DEF with the same tool, eliminating the need for two separate tools. This tool displays the condition of ethylene glycol and propylene glycol, and can scale to show the charge state of battery fluid. Users can confirm proper concentration of DEF (urea) and easily calibrate with distilled water. This tool is hand-held, works with ambient light and doesn't require power. The tool comes fitted in a plastic case.