Because strong athletes need strong rollers not foam pool noodles.
Two different grids for different effects or muscles.
A smaller grid for releasing bound up soft-tissue on smaller muscles or the heavier grid for larger muscle surface areas. You can choose the grid that best suits your needs!! The inside of the rollers are reinforced with plumbers’ concrete and a PVC plumbing fitting to increase their strength.
Remember, roll along the muscle fibers for gentle stretching and mobilising of tissue BUT ROLL ACROSS THE GRAIN OF THE MUSCLE FIBERS to make big changes to tight tissue. Do one spot (x 5-30 rolls), move along the muscle and repeat as necessary.
Or to really "release" muscles after the gentle rolling, use the Pin & Stretch technique. Find the tight spot that you felt when rolling, pin it down onto the roller and then move through a range of motion 3-6 times. Exhale on the eccentric/stretching portion and inhale on the concentric portion. I tend to favour Pin & Stretch over mindless rolling...but I recommend doing some rolling to initially loosen the muscles and to find the tight points that need to be pinned!