The Elements 4.5" Round Optimo Lens Hood Only is required to use filtration for 4.5" rounds. The new O.D. of the hood is 117.5mm, slightly wider than the stock hood. The factory hood must be removed before this filtration hood can be installed.
The original hood is mounted to the lens with a high strength thread locking compound. This bond can only break with heat. A heat gun is the best device for delivery and control of the heat however care must be taken not to overheat the interior of the lens assembly.