I have a toilet supply where an angle stop is threaded onto the end of a chrome stub coming out of the wall. I know of FIP angle stops, but those are usually one piece designs. It appears that this angle stop has an independent nut on it that would allow the stop to swivel to the correct position.
Can anyone confirm what kind of angle stop this is? See attached photo.
Due to the threads on the chrome plated nipple, I think it is just ordinary NPT thread. Probably 3/8, which is 0.675 inches OD, but could be 1/2, which is 0.840 od.
To unscrew, you can undo the flex line. Then hold the chrome nipple, and I would use a curved jaw locking pliers for that.
What I did is to just turn my valve not holding the nipple, and the nipple unscrewed inside the wall. That was my desired thing, because I wanted to be rid of my galvanized nipple, and put in brass. I have since bypassed that steel pipe in the wall, and use PEX to my valve.
Just turning the valve might not be a good idea if you did not know that you had steel pipe in the wall.
Are you just looking to have the output point some different direction? You could maybe tighten 1/4 turn. So what is your objective?