Quote: (Originally Posted by
londonsean69)

IIRC the SP MK25 and Apeks are
not the same, the SP is MUCH smaller
Have a look here
Untitled Document
and here
http://www.frogkick.dk/manuals/
If you try and service your own bits and they fall apart, it's your own fault, especially if you are using the wrong o-rings

Well, small correction here. When I wrote 'interchangeable' I mean - Can I replace o-ring with new one from service kit ? Of course I don't want to use Apeks o-rings in Scubapro regs etc.

Anyway thanks for reply I modified my question to correct one.
I just thinking about lifetime of first stages. If this o-ring is not interchangeable then lifetime will be probably shorter than classic regs without swivel. I never serviced DST/MK19/MK25, just FST and DS4 and 2nd stages - it's why I'm asking.
In near till I will buy few new 1st regs for stage bottles and I not decided to stay with DS4/MK17 or go to MK19/MK25/DST.