Cam followers have an internal design very similar to that of a needle or cylindrical roller bearing.

Cam followers have an internal design very similar to that of a needle or cylindrical roller bearing. They are characterized by a thick walled outer ring that enables them to accommodate shock loads while reducing distortion and bending stresses. The outside running surface is crowned as standard. However, cam followers with cylindrical (flat) running surfaces are available for certain applications. Instead of an inner ring, cam followers have a solid stud (pin) that is threaded so that the cam follower can be quickly and easily attached to appropriate machine components by means of a hexagonal nut. Axial guidance for the outer ring is provided by an integral flange at the head of the stud and a flange ring pressed onto the stud, or by the roller complement. Cam followers are pre-greased ready-to-mount units that are suitable for all types of cam drives, tracks and conveyor systems.

http://www.gwllb.com/product/443-stud-type-track-rollers---f718/

Stud type track rollers