Newly Rebranded by GRONK Fitness Products. Gronk Fitness Products is Football Star Rob Gronkowski’s new line of equipment designed for sports performance training. Chin-ups are arguably the best upper body resistance exercise around. There is no other exercise that can replace its functional value; and no, the lat pull down is a not a suitable replacement. Not only do chins build the back and biceps, the abdominals, chest and grip get a workout as well. A chin-up bar in a gym is also a highly useful fixture, given that it can also be used as an anchor for rings, bands or a suspension trainer. The Gronk Fitness Chin Up Bar itself is bolted flush to the support brackets so there is no play or movement, just a solid fixture that will take any weight up to 800lb!