Good morning,
ther are two tipes of o2 jakets, manual and auto, the auto models have the hidro fiaring s previously mentiond. most of the new colars are easy to fild pack , and all have an oral inflator, its also very surprising how much flotation is gand with only a cupel of puffs of air in them .
thay need more mantanance than a PFD and must be servised yearly, with ther growing popularity hear in Australia it now OK for home servacing to be made on privatly yoused jakets , but for survay must be caried out by a recognised service center.
Ther is also a hibrid on the market to, Kokatat have ther sea o2 which is a pfd with half its flotation in foam and the rest with an air chamber . Im curently testing one now, and sofare im realy pleased , it lite non restrictive well made (this model is stil made in the US ! ) and easy to youse 90% of the time I wold never need the extra flotation, but its ther for when I do . the charge is instant , and with 3 pufs its up enough to.
If you go down this road make shore to realy consider what tipe of inflator you get, my preferance is manual ,less chance of it inflating at the rong time , sumtimes the hidro plugs in the mecanisam can be more tuchie than others.
hope all your trning is up to pace
best regards Mick MacRobb
flat earth kayak sails