The hot runner design should be balanced for even flow throughout the runner system. Externally heated manifolds work the best for RTP TPE materials. Internally heated systems, which use cartridge heaters, are not recommended as they generally have hot spots which could lead to material degradation. All flow channels should be highly polished with radius corners to minimize the possibility of material stagnation. To maintain high shear, low residence times, and provide for self-clearing, the flow channels should have be 0.250 to 0.375 in (6.35 to 9.52 mm) diameter. Balance volume per shot size.