Received recently the Nikon CFIUW 10x/25mm eyepiece off eBay.
(Corrected Focused Infinity Ultra Wide)
The performance of this eyepiece excellent with about 20mm of eye relief. It is pretty much the same as the 12.5mm I bought earlier except off axis the pin point stars are very good out to the last 5%+or-.
This one came with the 30mm barrel so I had to trim a couple of mm off my Tak diagonal compression ring to allow it to tighten enough to grip the barrel.
Did a quick flashlight test and looks to be about 55deg afov also. (Ultra wide for a microscope eyepiece)
Size comparison against some others- it’s tiny!