They have an extended thread so that if a very hard knock damages the thread, the front can be faced back a little to expose fresh threading. Note how I wasn't being dainty about handling the scope with one fitted - I was very surprised at how strong those fine threads are.

A video imparts more than text and photo's can so have a quick look - It starts with the last production stages in a CNC machine that cost about £40K.
They are available now and introduced at £24 each - or £34 with a Floplas fitting that has had the moulding marks and ribs machined off + £6 RMSD.
https://youtu.be/QGB_nFx_KIU
Finally - some photo's:


