The 'dip' exercise is great for the chest, shoulders, triceps and rhomboids. Training this movement regularly can bring the desired physical results. As one gets strong there eventually becomes a need for a waist belt for adding resistance to progressively overload.
The hand is innervated by three nerves - the median, ulnar, and radial. As one becomes extremely strong the ulnar nerve tends to be susceptible to the added pressure of weighted dips, which causes pain in the heel of the hand radiating upwards towards the elbow. This nerve compression and uncomfortable feeling does not allow an individual to continue making progress with the exercise.
Having a dip bar that has a larger than normal circumference takes stress off the nerves in the hand and allows an athlete to Get Strong!