Weigh Safe trailer hitches have a built-in scale to measure tongue weight to ensure safe towing. The Weigh Safe Drop Hitch effectively measures the tongue weight of your towing load, ensuring that your vehicle is balanced properly and is safe to tow. Pressure on the ball sends a reading to the built-in scale that measures tongue weight (lbs.) For proper towing tongue weight should be no less than 10 percent of gross trailer weight (GTW) and no more than 15 percent. For example, tongue weight for a 10,000 pound trailer should be no less than 1000lbs. and no more than 1500lbs.