on the brand and model of it. In general these pipes are made to withstand 35 pressure bar with inner internal diameter. – HP pressure gauge or flexible flexibles (for high pressure): These types of hose allow to connect the manometer to the 1st floor. It can also allow to connect the wireless air management transmitter. They bring the high pressure from the 1st floor, which is in your diving block. These HP hoses are made to withstand high pressures (1250 bar) .- Inflator hoses, also called DS flexibles (for Direct System): they allow to connect the inflator of your vest on the 1st floor of the regulator . They disperse the average pressure from the 1st floor and are made to withstand 35 pressure bar.How can we identify the different types of hoses? 1) The 1st floor connection: the 1st floors of regulators are equipped with 2 types of connections (We are talking about connections ports): – MP ports (medium pressure), often 4- HP ports (high pressure), often at number of 2 to avoid a risk of connection error (connect a flexible MP on an HP port or vice versa), MP ports do not have the same diameter of no screws as the HP ports. Different types of connections: In order to better understand the characteristics of the different connections of the hoses, it takes all First specify that by diving all these connections are made with the inch (1 inch = 25.4mm) unit and the screw pitch is expressed in UNF which means “Unified National Fine”. It is something amazing because the 1st diving regulators have been manufactured and marketed by French.Concence the average pressure, most 1st stages have 3/8 UNF ports. This corresponds to a diameter of 3 / 8th inch, or 9.53mm. On the other hand, some manufacturers (including Mares) have some of their models from a medium pressure port with a larger diameter. For summary, on some 1st floors it is possible to have 3 MP ports in 3/8 UNF and 1 MP in 1/2 UNF corresponding to a diameter of 1/2 inch, or 12,70mm.For the high ports Pressure, they are in 7/16 UNF, which equates to a diameter of 7 / 16th inch, 11.11mm.2) the connection side 2nd floor and instruments: on the flexiblela connection side 2nd floor manometer or Inflator is of female type unlike the 1st floor connection. For the largest part of the regulators it is a female connection in 9/16 UNF (14.29mm in diameter). To ensure the sealing with the 2nd floor, there is then a male cylindrical part inside with an O-ring that you can grease slightly at the time of assembly. It is important to emphasize that some models of certain brands have a proprietary connection.