This red electro-hydraulic hydrometer is a dedicated measuring tool for lead-acid car batteries, used to test electrolyte specific gravity to judge battery charge level. Its transparent red outer tube makes internal float readings clearer and less prone to wear during daily inspection. Equipped with a rubber suction ball and anti-corrosion sampling tube, users can easily extract battery electrolyte for quick detection. Built-in precision floating scale provides accurate density data, helping users identify undercharged, fully charged or failed batteries in time. The whole device adopts acid-resistant plastic material, effectively resisting corrosion from sulfuric acid liquid. Lightweight handheld design is convenient for auto repair shops, vehicle maintenance stations and battery factories. Simple operation without complicated calibration. With stable test performance and competitive wholesale price, it is an essential detection tool for automotive maintenance distributors worldwide.