Designed as an RxClip replacement for the Shimano range of cycling glasses: I found the retail RxClip had an unusable and unsafe distortion amount with moderate to high nearsighted prescriptions due to the lenses curving around with the main lenses - this design flattens the lenses and gives me pretty much perfect vision using the same lenses I had made for the RxClip (I'm -6 in both eyes as a point of reference).

Just to avoid any confusion - it's just the insert not the glasses frame too - ie the separate black item on the plate in the photo. The white print installed in the glasses is t-glase which seems a pretty ideal material for this item.

It is designed to be mounted using the metal bracket that comes with the glasses and previously held the rubber nose piece - gives a very solid install.