The 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.

FEATURES

First stage (R-600)

>	Ultra-compact balanced diaphragm first stage
>	EK-600 cold water kit available for temperatures below 50°F/10°C
>	DIN-R600 conversion kit available (300bar/4350psi)
>	2 HP and 4 LP ports

Second stage (S-81)

>	Elliptical low-profile case design
>	S.E.A. – Sequential Exhaust Assist technology (Pat P.)
>	Venturi adjustment lever
>	Built-in moisture exchange plate
>	Attached to MIFLEX® hose for exceptional flexibility
>	Breathing Resistance Adjustment Control
>	Ortho-consciously designed mouthpiece
>	Eligible for TUSA CARE Free Parts for Life Program - USA Only

TECHNOLOGY

TEFLON COATED PLATE TEST The Teflon Coated Plate prevents “dry mouth.” Condensation forms on the brass plate adding moisture to the dry air released from scuba cylinders.

CLICK SPRING ADJUSTMENT The Click Spring Adjustment feature is exclusive to TUSA. It is a five (5)-position adjustment knob designed to better control breathing resistance.

COLD WATER READY The Cold Water Ready feature enables the diver to use the regulator in water temperatures below 50° F / 10° C.

ENVIRONMENTALLY SEALED 1ST STAGE The use of a secondary diaphragm and piston sealing the 1st stage preventing contamination or freezing when the regulator is submersed in contaminated or freezing water.

ORTHO-CONSCIOUS MOUTH PIECE The Ortho-Conscious Mouth Piece feature prevents jaw fatigue. The ridges and flexible material allow the diver to have more control of the mouth piece and reduces tension in the jaw. Read more

SEQUENCE EXHAUST ASSIST SYSTEM The Sequence Exhaust Assist System gives the diver less resistance when exhaling due to its unique double exhaust design. The diver experiences smooth breathing cycles reducing air consumption and fatigue.

VENTURI FLOW ADJUSTMENT The Venturi Flow Adjustment allows for ease of breathing by controlling the direction of air through the mouthpiece.