In a jacket-style BCD, the inflatable bladder will be along your back and around your sides underneath your armpits. This is the most common style of BCD for scuba diving. Lift capacities are generally suitable for both warm and cold water diving. This style of BCD is great for newer divers who are just learning the "feel" of buoyancy because you can sense whether the jacket is inflated or defalted by the amount of air at your sides. It also is easier to float at the surface in a vertical position (head up, feet down). The disadvantage of this style of BCD is that it also tends to push you in a more vertical position underwater, making horizontal trim a bit more of a challenge. Also, the inflation of the bladder at your side can be uncomfortable and cumbersome for some.