Runner is also called horizontal runner and is the channel for molding material from Sprue to female mold. Runner normally needs be solidified before taking out, so the runner is cut into two halves at the diameter line for processing then match up. Base on the fluidity, section shape of runner, there are round, U, Trapezoid, rectangular and square shape. Round and semisphere and trapezoid are the better ones. But in the fluidity and heat dissipation, round runner is the best. The next are rectangular, trapezoid and square. Semi-sphere is rather less used except in special circumstances. The benefits and shorts are as the following.