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Guest
Is it?
I thought the 555 was non user adjustable while the S600 is adjustable. To me that is a huge difference.
It is. Many divers do not see the value in the user adjustment. But I find mine to be very useful in currents and surf, and to maximize performance. All of my alternates are user adjustable which allows me to turn them down when not in use to avoid freeflows and still have top performance when in my mouth. Plus, I don't believe the S555 has the seat saver feature. That feature is not to important if you service annually, but I tend to go 3 to 5 years between replacing seats on my balanced poppet regs.