This Unbreakable handy battery hydrometer allows you to accurately check the specific gravity of lead-acid batteries like those found in cars, trucks, motorcycles, boats, and backup power inverters. By measuring the density of the electrolyte solution inside each cell, you can determine the battery's state of charge and whether it needs to be recharged or replaced. Its easy-to-read analog scale makes for quick, no-nonsense readings that you can use to proactively monitor your battery's health. Designed to work with common lead-acid batteries, this hydrometer pays for itself by preventing unnecessary replacements down the road. Keep it in your toolbox or vehicle to test batteries with just a few drops of fluid - it's a simple yet effective way to optimize battery performance.