The Scupper Valve (SV) design is self-draining and delivers crisp, effortless clearing. Posi-lock flex retainer secures flex section and mouthpiece. Dual silicone mouthpiece prevents over-clenching of teeth that would restrict air flow. Rotational mouthpiece with ratchet indicators. SV2 Semi-dry top is designed to limit splashed water from entering the breathing tube.