: Peter,
: I do not own the Porter Cable but I have a Dewalt with the same feature and
: when the replaceable plastic ring goes, you will know how well it was
: working! She whines and does about 60000 rpm.

So that's why the bottom half of my Dewalt sander pad went flying across the room. The sander is about 3 or 4 years old and I let someone use it who sanded on the edge of the pad causing the plastic ring to be exposed. It finally fell apart. The replacement pad seems like it's made from a better compound than the original.

Kurt