So this is a great product and is very secure when wearing. I got the small that allows for a bit of growth in the cage (for me anyway) but not to get to what could be classed as full length. I have had padlock cages before but with how this one is positioned there is literally no movement/rattle from it when moving.
What the photos and info don't show is there is a D shaped piece of plastic on the bottom of the ring and that faces towards the rear. This is not a massive problem but wasn't what I was thus expecting when I received it.