This is my first experience with a field flattener. So I can't compare it with any others. But it looks like it works well. It definitely makes a massive difference to the way the stars look. Pretty much sharp all the way to the corners. Am still assessing and searching for the optimum setup, so hopefully can improve it further..
I am using it with a StellaMira 66mm f6 refractor. I am finding that, when connected to that telescope, it seems to need much greater spacing than the advertised 55mm. In his review of the telescope, Bryan suggested he was getting good results with a spacing of 70mm. I seem to be homing in on a similar result. So far, for me, the good region seems to range between about 65mm and 75mm. More testing is needed to refine that. It definitely isn't good at 55mm. Am reporting that in case it is helpful info for others. And giving it four stars as it seems unfair to give it five, because of the spacing issues!

This works really well with a Starfield 102 ED and being able to hold a 2 inch filter is a useful extra bonus.

Used with Stellamira 80mm F6.25 for photography at the required 55mm backspacing + Optolong L-Pro + modified Sony Nex-5N does exactly what it is meant to at a most wonderful price!

Stunning and very well built.
I got this to go with the Stella Mira 90mm for extra targets. Simply screws onto the scope with the spacers supplied with your camera, switching one equal to my filter drawer and add 533mc bring to focus and perfect performance. Beautiful flat field and crisp sharp stars all over. Single 2min sub on Andromeda fill the field diagonally. Stunning capture.
Thanks FLO for top quality gear and top quality service.

Produces a nice flat field with my Z5 full frame mirrorless camera and Sky-Watcher Evolux 62ED

Well I'm please with my results of The Orion Nebula and Horsehead nebula. Glad I have my optical train now set up correctly

I've only had the opportunity to use this once so far, it appears well manufactured and fits the end of my Startravel 120T focuser. The 2" push fit makes attaching the CCD to the OTA a lot easier than having previously had to screw on the imaging train to the OTA. Intial images show that there is clearer focus at the edge of the FOV so I guess it is doing what it is supposed to be doing.