CoolFlow nozzles are designed for long service life and better heat transfer, using state of the art computer modelling to analyse the cooling water flow and heat transfer from the plasma arc. CoolFlow nozzles benefit from the following features to provide excellent performance and longevity. Solid head improves conduction cooling and excellent shield alignment. The O-ring is positioned back out of the hot zone for improved sealing, reliability and robustness to leaks. An optimised cooling groove is designed to minimize coolant stagnation and maximise convective cooling to keep the nozzle and seal cool.