3M Hookit 6" Half Round Pad
This is one
The pad is fairly rigid, so don't expect a lot of flexibility. The 6" radius allows discs to contour to large areas, such as hood bolsters, or flared fenders. Works nicely with film backed discs, but much better if the disc has some built-on cushioning.
Not an exact fit for 6" discs- it's as if someone didn't account for the 1/4" radius, but this 3M model is the best fitting and thinnest I've been able to find. Another high quality product from 3M.
Looking for a round yet flexible hand pad?Check out the Mirka E6HP 6" Ergonomic Hand Pad
Check out the 3M 05791 6" Hookit Flexible Hand Pad.
Looking for a round & firm hand pad?
Check out the Meguiar's S6HP 6" Diameter Palm Grip Hand Pad.
Convert 6" discs into a double edged sanding block: