Measures the freezing point of coolants and concentration of Ethylene/Propylene Glycol. This Extech RF40 portable battery coolant/glycol Refractometer is easy to operate refract meters provide accurate and repeatable measurements on easy to read scales. The RF40 measures the freezing point of automotive coolants (propylene glycol and ethylene glycol) and indicates the specific gravity of battery acid and provides a quick reference of battery charge condition.