F.A.I.R. first came into the US through New England Arms bit more than 20 years ago. I own a NEA 500 in 16 ga. They are CNC made with tolerances close enough that you can order a second bbl. and in most cases it does not need fitted to the gun. I have 28" and 30" bbls. for mine.
The 30" I use for clays on occasion I used to shoot it a lot at one time. Hard to tell exactly how many rounds through it somewhere between 15K-20K. Never had any problems with it. The 28" I use for ruff grouse.
Their next venture was with BC Outdoors and the Verona models. Bought my son his first 12 ga. a Verona 5xx O\U don't recall the exact model number ~15 years ago. Never had any issues with it either.
Also own a F.A.I.R. Iside in 16 ga. Just the basic model but I shoot it extremely well and it is my favorite grouse gun.
Good chance my next gun will be a custom order F.A.I.R. much like Vol423, a 28 410 combo. Except it will be Gardena wood (Beavertail & Pistol) with 30" bbls. for clays. And a single trigger with extractors. And upgraded wood.
There are 6 of us that shoot together as often as we can, scattered over a fairly large area. But usually squad together when at least 5 of get together. Out of the 6 of us 5 own F.A.I.R. Isides and some multiple FAIR Isides in different gauges. The 5 of us all have at least one Iside 16 ga. and one gentleman just placed a custom order for his second 16 Iside. They are a great gun IMO.