This dual-scale handheld optical refractometer is specially engineered for automotive maintenance, supporting two core test ranges: -50℃ to 0℃ antifreeze freezing point and 1.00–1.40 specific gravity for lead-acid battery electrolyte. Built with premium wear-resistant optical prism and built-in ATC automatic temperature compensation, it automatically offsets temperature interference to deliver instant, precise readings without extra power sources. The lightweight aluminum body with anti-slip rubber grip fits one-hand operation perfectly for garage, roadside and fleet inspection. Simply drip coolant or battery fluid onto the prism to read data clearly through the optical eyepiece. It accurately judges antifreeze anti-freeze capacity and battery charge status, helping mechanics avoid engine frost damage and battery premature failure. Compact, durable and low-maintenance, this all-in-one tester is an essential diagnostic tool for auto repair shops, truck fleets and DIY vehicle maintenance enthusiasts.