From the Photo Warehouse site:
"Xtreme 400 is a high speed, medium contrast film allowing for exceptional utilization in action and sports photography and also an outstanding selection for general purpose photography. With a standard rating of ISO 400, it provides negatives exhibiting incredible sharpness and yet retains a fine grain under a myriad of lighting conditions. Xtreme 400 was designed to react vigorously to push processing and film speeds up to EI 1600/33 are easily achievable with X-tol type developers, maintaining nice shadow detail and perfectly scaled mid-tones, while still maintaining grain structure."
The film has a very good representation in the Massive Development Chart, meaning it's likely that you will find your choice of developer for this film.
Now I have only shot this film at the box speed, and in a recent trip to Oregon, I shot a few rolls in my Yashica FX-7 and Olympus Trip 35.
A few examples from the Trip 35 developed in D-76 1:1 for 14 minutes-
|Portland Art Museum|
From the Yashica FX-7, all from downtown Portland, developed in Rodinal 1:25 for 7.5 minutes:
More Portland images from the FX-7, but developed in D76 1:1 for 14 minutes:
I am really pleased with the results thus far. My only complaint is that the bulk roll did not come on a core, and I don't know if that will be a problem or not. I like the fine grain, and the above images required very little tweaking in the scans. Another nice feature - the film lies absolutely flat in the scanner film holder. There is no cupping or curling. Another nice feature -- a roll of 100 feet is $35 US. Ultrafine Xtreme 400 is an excellent 400 ISO film that can be pushed to 1600 (which I need to try) at this price is quite amazing. If you don't want to roll your own, you can also buy it in 12, 24, and 36 exposure rolls at about half the price of a roll of Tri-X. I'll try processing my next roll in the FPP Super Monobath and see how it goes. I'm not going to guess who supplies the film stock. The rebate has Ultrafine Xtreme 400 printed on it. I'm happy with it, and it doesn't really matter who originally made it -- Photo Warehouse has been selling it for a few years, and it's a great film to shoot with.
UPDATE - 06/25/2018
I demonstrated the FPP Super Monobath at Photostock 2018 on 06/23. I shot a couple of rolls in less than an hour with my Nikon F3HP in Harbor Springs. It happened to be a rainy day and the Farmer's Market was taking place in town. I used one of the rolls in my demo and it came out great. The standard 3.5 minutes at 74F. Here are a few scans of the negatives: