The Hollow Roller is a great deal. For the price of one, you get two: a classic smooth foam roller that fits into a 13-inch “The Grid”-like black, ridged foam roller, so you can choose the type of muscle penetration you need.
Both foam rollers are firm and able to remain in size while using. The black one with the knobs can be used to specifically access pressure points and provides deeper penetration. The orange one is smooth but firm as it needs to be to put pressure on various sections of the back and spine.
The orange foam roller fits into the black one, which makes it easy to pack both into your gym bag. The hollow roller is 13 inches by 6 inches and the foam roller that fits inside the hollow roller is 13 inches by 5 inches.
On Amazon, the Hollow Roller has a solid five star rating (over 81% of all reviews are five star).
If you are looking to get both a soft foam roller and a harder one, this is a great combination. If you prefer a single foam roller, get The Grid instead (see our review).