I bought this to replace the tightly moulded plastic hook on my Selmers MKVI Tenor, which I found with uncomfortable and in the wrong place!
The 'forza' thumb rest seems rather expensive for what it is I know, but it's been a game changer for me! It is more versatile in terms of position options, and as it can be 'opened up' away from the body tube, it gives me a much more natural and comfortable position. This also aids dexterity. Having used this for a coupe of years now, I would not be without it!