These are the best battery ends around and install in seconds. The solder and flux are pre measured and loaded in the barrel of each connector. Just heat connector with a propane torch and slide cable in. For a professional result, add the Fastronix Heavy-Duty Heat Shrink and you'll have a totally sealed bullet proof connection. Fittings are polarity specific for a perfect fit, and constructed of tin-plated cast copper for superior conductivity and are available in straight, angle, flag as well as lug end configurations.