A muscular imbalance typically exists between the shoulder internal rotators and external rotators. The majority of lifters need to stretch the internal rotators and strengthen the external rotators. The ShoulderHorn is a device that isolates and strengthens the external rotators in an abducted position. By supporting your upper arms, it isolates the infraspinatus and teres minor and takes other shoulder and upper back muscles out of the picture. You can do pretty much the same thing by using a preacher bench. Just sit on the bench facing the opposite way with a pair of dumbbells in hand, rest your upper arms on the pad, and go to it. Remember to stretch the internal rotators between sets.