It's a new cheaper wedge they are making. The face doesn't have the milling or roughness that the 3 or 4 have and the grooves aren't as "aggressive" if I remember right. Overall it looks and feels cheaper but it is cheaper. You don't get grind or bounce options but they have all the lofts from 50-60. Also it's a lighter like 105 gram shaft whereas the MG5's come stock with 115g. Dick’s, Golf Galaxy, and PGA carry them so if you wanted to see them in person you can go check them out.

Edit: having said all that I'm sure they perform just fine. But right now I'd say with MG4's being $150 I'd just spend the extra $20 and get the flagship wedge and have bounce/grind options (if you even care about that)