The circular connectors in the Marine series are extremely resistant to corrosion, even in seawater applications, as Hummel's salt spray tests have proven: the connectors from French subsidiary Jaeger Connecteurs were sprayed with salt mist for 1000 hours. The reason for the resistance is a copper-nickel-zinc alloy called 'Arcap', from which the connectors are made. The alloy is non-magnetic, as it contains no iron, and is resistant to chemical corrosion, oxidation and large temperature fluctuations. In addition, the circular connectors are waterproof up to a depth of 100 m and work reliably at temperatures from -40 to +100 °C. The range includes cable and coupling connectors as well as device connectors with flange or rear wall mounting. The contact inserts in the series enable a range of three to 37 contacts. These are gold-plated brass contacts in a neoprene insert.