Metal o rings are also used for mould application especially in the hot runner moulds to seal the leakage between hot runner manifold and the nozzle. The commonly used sizes for this type of application are 12.7 mm OD and 16.1 mm OD. These seals are vented (small hole on ID) for internal pressure. Various other sizes can also be made as per the requirement. One seal is required per nozzle and has to be replaced once the mould is opened. These seals are for, “use and throw” application i.e. it cannot be reused.