By inflating the BC at the surface, a conscious diver may be able to easily float face-up, depending on their equipment configuration choices. A fatigued or unconscious diver can be made to float face up at the surface by adjustment of their buoyancy and weights, so the buoyancy raises the top and front of the diver's body, and the weights act at the lower back of the body. An inflated horse-collar BC always provides this orientation, but an inflated vest or wing may float the diver face-down if the center of buoyancy is behind the centre of gravity. This floating orientation is generally considered undesirable and can be minimized by relocation of some of the weights further to the rear, and using higher density cylinders (typically steel), which also move the center of mass towards the back of the diver. The BC type can also be selected with this factor in mind, selecting a style with a center of buoyancy further forward when filled, as this has the same net effect. Any or all of these options can be utilized to trim the system out to its desired characteristics and many factors can contribute, such as the number and position of diving cylinders, the type of diving suit, the position and size of stage cylinders, the size and shape of the diver's body and the wearing of ankle weights, or additional dive equipment. Each of these influence a diver's preferred orientation under the water (horizontal) and at the surface (vertical) to some degree.