The bushing on the left is a factory zero degree piece from an axle. The center and right ones are two styles of aftermarket camber bushings. These are available as fixed angle bushings in fractional degree steps up to about 3 to 4 degrees. There are also adjustable bushings that allow a range of movement, and the bushing is then locked in position. Adjustable bushings affect caster angle as well if the bushing is rotated to some setting other than the maximum angle.