The Titleist MB 712 irons replace the 710 version and according to Titleist the MB iron is their most popular model on the PGA Tour.
To be honest we are not surprised as not only is it a good iron, but also because you need to be highly skilled player to get the most from them. This is a very traditional blade and performs very well provided you hit it out of the middle and this is where things get a little sticky as the sweet spot is quite small and the forgiveness is pretty minimal, so at least you get great feedback on how well or otherwise you have hit it.
Compared to the previous version the Titleist MB 712 irons have a nicer satin finish that looks a little more contemporary than the previous polished chrome look.
The tweaks to the sole design and the heel and trailing edge relief do make this a lovely iron to hit, especially from tight lies. It also enables a little more mass to go into the muscle back behind the face for a more solid feel.
Overall this is an excellent elite players blade iron but probably a little too demanding for virtually all amateurs, who would be better going for the Titleist CB 712 irons which are a little more forgiving with similar Tour level performance.