The WO GT81 is most likely the same objective as the 80mm f/6 triplets sold by TS and Astrotech/Astronomics.
TS says the 2.5 flattener and 3" reducer are good for FF.
The focusers vary on these models with a shift towards a newer, cheaper style where the pinion body is cast into the focuser (eg. WO GT81). Note that the TS picture still shows a separate pinion body which is easier to adjust.
https://www.teleskop-express.de/shop...cts_id=3881#cs