kckskh:
wat type or back plate and wing? Is the aluminim backplate from dive rite good??
I have been looking at a BP/W setup, and have been asking some of the same kinds of questions for a little while. So I'm no expert, but here's what I have been doing.
I suggest checking out the pretty pictures and the little blurbs that the manufacturers publish on the internet about their different rigs - those just suggested above, Dive Rite, Halcyon, OMS, Oxycheq, as well as Deep Sea Supply (often referred to as DSS here), Hammerhead, and there are others that you will run across when you start looking into your options (Fred T is another often mentioned here; he doesn't have a website, but he will email you information about his gear if you request it
ftagge@goldinc.com).
You will find backplates made out of stainless steel, aluminum, and plastic, and the differences in weight can be considerable. Some will offer stainless BPs in different thicknesses and weights.
The manufacturers will (usually) say whether you require a single tank adapter (STA) to dive single tanks on their BPs, and what they weigh (cut into two pieces to reduce weight, or a single piece which may also be in lighter or heavier weights, for example).
The reasons for choosing different materials may vary, but weight is a primary consideration. If you need to carry x pounds of weight, and you can put 6 pounds of that into a stainless BP, that's 6 less pounds to carry on a weighbelt or harness (and can also distribute better over the length of your torso).
There will be other differences between backplates (what steel exactly, whether the slots in steel have sharp edges that wear on the webbing or rounded/shaped edges or - like the DSS - have plastic inserts in the slots to protect the webbing from the edges), and a dozen other smaller points of differences that may or may not be important to you.
You can't assume that the wing from one manufacturer will fit on anybody else's BP - maybe it will, but maybe it won't. So you have to pay attention to the differences in wings and their features. For single tanks, I see a lot of people who really favor the donut shape (e.g., Halcyon Eclipse and OxyCheq Signature), but others who say that "non-donut" wings work just as well.
And then there's that whole harness thing ("Hogarthian" single continuous piece of webbing vs. whatever isn't).
I haven't seen any reason to think that the backplates from *any* of the names mentioned above aren't perfectly good products. But there are differences between them, and for what is actually a pretty straightforward piece of gear, you may be surprised at the differences in price from one place to another.