This mouthpiece fits all brands of regulators we sell and modern models from most other brands, except Poseidon. Available in hypoallergenic black silicone, we also include a tie wrap. (The fit on some very old models from the 70's and 80's with slightly smaller openings such as the old Aqualung metal second stage bodies are a bit loose and you should use a standard tie wrap pulled very tight or a SeaCure #1 mouthpiece.)