Check the listing for details. Tusa RS-681 Regulator with First and Second Stage. Condition: New. Listed at 719.00 USD. Tusa RS-681 Regulator with First and Second StageSKU: TBTRS681BKMfr. Part: RS-681U-BK DescriptionThe RS-681 is TUSA's latest regulator that delivers superior performance and build quality in a compact lightweight design. The R-600 paired with the newly developed S-81 second stage further pushes the regulator engineering and performance envelope. The ultra-compact balanced diaphragm R-600 first stage is incredibly small and weighs only 630g. The R-600 is configured with 2 HP and 4 LP ports allowing for versatile hose placement. A DIN conversion kit (DIN-R600) and an environmental kit (EK-600) is also available. The newly designed S-81 second stage offers the following features: S.E.A. - Sequential Exhaust Assist The Sequential Exhaust Assist (S.E.A.) is a revolutionary new second stage design featuring a dual exhaust system. The S.E.A. system consists of an enlarged primary and an auxiliary exhaust. The auxiliary exhaust, located on top of the S-81 elliptical case, works in conjunction with the primary to significantly decrease exhalation resistance. Exhalation resistance directly affects the diver's natural breathing cycle. By reducing this resistance or increasing exhalation performance, the diver breathes more naturally and comfortably reducing respiration rate and air consumption. Paired with the R-600 first stage, the S-80 offers a seemingly effortless underwater experience regardless of the workload. Venturi Adjustment The addition of a venturi adjustment lever on the S-80 allows the regulator to power assist the diver when underwater utilizing the natural venturi effect. The diver can also adjust the lever to prevent free flow such as on a surface swim. Moisture Exchange Plate The S-81 second stage incorporates a moisture exchange plate that captures condensation produced by inhalation and exhalation efforts. This condensation increases the humidity of the air breathed and helps to reduce that "dry mouth" sensation often experienced while diving. Breathing Resistance Adjustment Control The Breathing Resistance Adjustment Control on the S-80 allows the diver to simply adjust the flow of air according to their needs. The easy-adjust multiple click knob allows you to quickly and finely tune resistance. Miflex Hose The Miflex hose is light weight and extremely flexible. The multi-layer construction shows excellent abrasion resistance and allows for a longer lifespan found in traditional hoses. This kink resistant hose offers a burst resistance twice that of traditional hoses. The Miflex hose is certified to EN250 standards.FeaturesFirst stage (R-600) FeaturesUltra-compact balanced diaphragm first stageEK-600 cold water kit available for temperatures below 50 Degree F/10 Degree CDIN-R600 conversion kit available (300bar/4350psi)2 HP and 4 LP portsSecond stage (S-81) FeaturesElliptical low-profile case designS.E.A. - Sequential Exhaust Assist technology (Pat P.)Venturi adjustment leverBuilt-in moisture exchange plateAttached to MIFLEX hose for exceptional flexibilityBreathing Resistance Adjustment ControlOrtho-consciously designed mouthpieceMFG Lifetime Limited WarrantySpecificationsMaterialChromed BrassStage TypeBalanced DiaphramLP Ports4HP Ports21st StageAdjustableYesStage TypeDownstream Demand ValveHose Thread3/8"Hose Length30" (75cm)2nd StageTotal Weight38 oz (1,058g ) Feedback is a very powerful tool. It gives sellers a reason to conduct business at the highest level of honesty & respect. 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