Without pictures we will all be guessing, just like you.Zippy : I found some small hard white chunks of 'I don't know what' in one of the piston bores. A few little pebbles of rock hard white material that could be plastic. The brakes have not been apart before. I added Galfer lines a couple of years ago, and speed bleeders. I did not seem to hurt things, but I think it's odd. I don't think it is teflon thread sealer tape, because it is hard. I did also see a small bit of what I do think was teflon tape. It was stringy and not hard at all. It's never been down, and the master is in good shape. Any ideas? No big deal but I am curious as always.