NOTE: The “Fitting DR” is the DR of the base fitting from which the fitting is made. This DR is the DR of the piping system for which the base fitting is appropriate to use. The “End DR” is the DR of the ends of the fitting. If the End DR is larger than the Fitting DR the ends have been machined. The “End DR” governs the “rating” of the fitting. Best practice to maximize the life of the fusion between the pipe and the fitting and to reduce the variables present in the fusion process is to match the DR of the ends of the fittings to the DR of the pipe to which it is fused.