High efficiency is claimed, but looking down the list of applications suggests it is around 50% – rather than the ~90% Ledil collimators generally achieve. Maybe the sharp cut-off has something to do with this.
Looking at the data sheet, it looks like surrounding the central clear window (not a hole, and the photo might suggest) is a Fresnel lens – take a look here.
Overall the optic is 50mm across and 53mm with its holder.
Looking at the plots, it looks very much like the beam has a slight offset to one side, keeping it in contact with the wall if the holder axis is mounted parallel with the wall surface. The website does say “an additional sub-lens helps to achieve virtually limitless creativity in lighting by shaping the beam from ultra-narrow spot to a high aspect ratio oval”, which might be a reference to this.
Looking at the holder drawing, the centre of the led and the centre of the lens are offset from one another, so getting the holder orientation right is important, and it might be a symmetrical lens – I will contact Ledil seeking clarification.