Review on Sackorange 5 inch Hook and Loop Hand Sanding Block - Sanding Pad - Hook Backing Plate for Sanders/Polishers by Greg Lockhart

Although I like the idea of this sanding pad, the problem is that the bottom of the sanding pad (the part where the sanding disc is attached) is not flat - it curves into a convex shape. So when you attach a grinding wheel, the only part of the grinding wheel that comes into contact with the surface to be ground is exactly the center of the grinding wheel. If you push very hard, the entire wheel will make contact with the surface being sanded, but 1) it tires quickly and 2) you'll end up sanding much more aggressively than you'd like. This might be fine for aggressive sanding, but for things like sanding scuffs between coats of paint/finish or areas that require a softer touch, this isn't the best option.