Adapter sleeves are the most commonly used components for locating bearings with a tapered bore onto a cylindrical seat as they can be used on:
plain shafts 
stepped shafts
They are easy to install and require no additional location on the shaft:
When used on plain shafts, the bearing can be located at any position on the shaft.
When used on stepped shafts together with an L-shaped spacer ring, the bearing can be accurately positioned axially, thereby facilitating bearing mounting and dismounting.