The main difference between all of the solid balls is the size. Each have a dense core and softer outer layer with a grippy texture. Their size provides a different stimulus for your tissues but they can be used interchangeably with the original YTU Balls depending on your desired pressure. The larger balls grab a hold of more area at once, so it may actually minimize the trigger point specificity that some people prefer with our smaller YTU balls. The different sized balls give you multiple options all over your body or within any given area. You will find that the ALPHA Balls are awesome on the chest and buttocks. The PLUS sized inside of the snug grip tote are perfect for rolling the back of the neck and creating maximum traction along the spine. Larger body types may prefer the PLUS and ALPHA over the originals, although the originals are important to access small, tight areas. We believe there’s different tools for different body parts and different desired depths of pressure and these three different sizes give you the tools you’ll need for a full body approach. Please do not use any of the Therapy Ball products directly on your abdomen; for abdominal massage, please use the Coregeous Ball.