The ALPHA BALL measures at a sizeable 3.5" in diameter, providing a massive amount of sheer and grip. It's ideal for areas like the QL, pecs, buttocks, hips and other large muscle mass; use it against the wall and roll along the chest, shoulders and scapula, or go deep into your QL, low back and hips. Its soft top layer and dense inner core allows you to roll over and around bony prominences -- there is absolutely nothing like it!