Progressive Bite Ring Progressive bite rings for use with Ermeto / Parker EO® hydraulic compression fittings and RS Pro hydraulic tube. Banjos, Bite Rings & Tube Nuts Ermeto Original or EO® progressive ring fittings, for metric tube, are manufactured from mild steel, with zinc plated and passivated finish. They are available in light duty and heavy duty series to cover a wide range of pressure ratings. Each fitting comes with a tube nut but the bite ring will need to be ordered separately. The progressive ring bite produces a keyed leak-free tube connection. The range of fittings is intended purely for the assembly of connections for fluid applications. All fittings are supplied with an instruction leaflet. For steel fittings it is recommended that seamless drawn steel tubes to DIN 2391/C are used. Operating temperature range without pressure reductions for the steel fitting material is -40°C to +120°C. Warning Hydraulic systems can work at high pressures. To ensure functional safety of EO® tube fittings, only EO® parts should be used in their assembly and the pressure and temperature ratings should not be exceeded.