DNP says its PLK4 series, that is "male" couplings equipped with a decompression system, allows the connection with a "female" coupling even in the presence of residual pressure from the male side. This series of couplings has been designed to be connected to the DNP PLT1 and PLT4 series, both manufactured according to the ISO 16028 standard. The PLK4 series is available from ISO 6.3 up to ISO 50, with a wide range of threads (BSP-NPT-SAE-METRIC) to satisfy every possible need.