Very sturdy. The construction feels solid and able to handle tons of practice rounds. I would not take this set into tournament play...even for amateurs.
The shaft and feel of the TaylorMade Rac's don't cast. You can feel the head all the way thru contact and actually feel a solid ball compression when you strike it squarely.
If you want to score low, you have to be able to control you ball flight path accurately and these irons give you an open margin of error of about 7 to 10 yards, instead of an exact pin high distance. When you strike the ball squarely, they can't guarantee the kind of english you'd get with a more bladed set. The face is nice, big and forgiving, but sometimes this can hurt you in your approach shots.
The Bottom line assessment of these Rac LT irons from TaylorMade is that if your just starting off and feel that you might shoot anywhere from 95 to 130, these clubs are great. The big open face is forgiving and you will get the ball in the air and give yourself a fighting chance. If you feel like your starting to play the best golf of your life, your handicap is closer to the single digits or low teens and you need pinpoint accuracy, a slightly more gunslinger feel and need to place the ball exactly where you aimed, which is always pin-high (as we all think we do), then these clubs aren't for you. Leave the big face and forgiveness for the tweens at the school yard and go out and buy yourself some R9's just like Sergio. If you're playing good golf do not buy these, they can only hurt.