Iím a little confused because Iíve seen Spinlocks in West Marine, so I would have thought they could get the correct cylinder for you. Have you asked?
Although there is some crossover, rearming kits are not universal. Iím sure WM donít make their own life jackets, so theirs is probably a Mustang or Sospenders or similar. Spinlock uses or has used at least two and I think three different triggering mechanisms (UML, Hammar and I think conventional).
There are only a few fittings for cylinders so you can often find one that, while maybe not exactly the same, will work. As an example, I have a European 180Newton lifejacket that uses a 38 gram cartridge with the smaller screw thread(I forget the actual thread size), which isnít available here (I have a couple rearm kits) but West Marine has a cylinder that is the same except it is 35 grams, which I figure I could use in an emergency (it would still give me about 165N of buoyancy or about 37 pounds Ė most adult U.S. sold lifejackets are specíd at 35 pounds). My jacket also uses a UML pro sensor which is now being used on some Spinlocks so I am hopeful that these are now available here and will fit, although I havenít tried to confirm that.
I have traveled with my lifejacket and a rearm kit and although it has been questioned, I have never had a problem. I always pack it with a copy of the TSA leaflet that says you can carry one life jacket and two rearm kits.
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BTW, 275 Newton jackets are intended to right an unconscious person in a survival suit but they also restrict your ability to move and help yourself. If you are not going to be wearing a survival suit or similar, you may want to consider something in the 150N Ė 190N range. I think Spinlock do a 170N jacket. Just something to consider. And while I'm preaching, crotch straps and spray hoods are proven lifesavers - I don't understand why they aren't universal.
You do know that most euro jackets are not USCG approved so, while it is legal to wear one, it doesnít count towards having a lifejacket for each person on board, right? And for comparison, 100 Newtons = 22.48 pounds of buoyancy.
'Hope that was of some help