Yes, FocusPLUS PRO be attached (as long as there is enough clearance) on either side of a lens.
Note: The FocusPLUS PRO only works with hard-stop lenses and infinity lenses. It is not compatible with Servo or Focus by wire lenses.
Hard-stop lenses: Mechanical focusing with a hard stop on the ends of focus limits. The focus wheel rotates for approximately 30 seconds or until it reaches a hard stop.
Infinity lenses: Mechanical focusing with no hard stops on the ends of focus limits. The focus wheel rotates infinitely without adjusting the lens elements.