Vertical Back Flag on rings and straps

Is anyone else training this move and can comment on the risks, preparation and common names used?  I have been seeing it a lot more lately in the street workout scene.

Very nice, I'm envious! 

I know it under the name of the meathook. If you use that search term, you should find a few threads about it. 

What would you say are prerequisites in terms of strength and mobility for this move? 

This position have some very "nice" risks and a lot of people perform it without a good preparation. 

it requires for sure biceps flexibility due to the torque on the grip , prone and supination mobility, supraspinatus mobility and some degrees of shoulder extension. without a good rotator cuff preparation the result could be dramatic. 

I think Mikael (Handbalancer) posted on this one a few years ago IIRC. Circa 2010-11 off the top of my head

That's called a reverse meathook or flag.

Thanks everyone.  I am not referring to meathook or reverse meathook as those positions are much more common and significantly less dangerous than pressing to a vertical body position as Alessandro notes.  You can see both a beautiful example of the move and some of why it can be dangerous in this clip by Igor Zaripov from 2008. Note at about 6:15 as the video cuts away when he almost jumps out of the position!  I assume he was jumping to the ground although it isn't clear.  I would like to start training the move more frequently however I need to have a better understanding of it first.

I have heard it called the kalashnikov by some straps people for some reason. My first coach called it the "shoulder trauma" haha. Its mainly a flexibility move. I havent practiced it for a long time, but I can only do it on my weak straps arm because the other is too stiff to reach the position. The easy version is to do it with 2 arms so the other arm is straight out in front of the body  This arm does very little if you get the arm behind placed correctly and its useful for preparing the shoulder to go the last few centimeters. You can(and from my perspective, should) cheat at it by getting a lot of friction between your back and the arm as you go into it so the weight isnt pulled only from the hand. 

You are doing it quite well, just a matter of going a bit deeper and cleaning the position. How is your 1 arm back lever? I usually would pull out of it into the lever as it seemed like the best option to get our of it.