I used the traditional felts until about 4 years ago then i went to the coconut felts however last year i had allot of eggs out the nest broken/cracked with the nest felts out as well, after days of trying to figure out in my opinion the birds toe nails were catching in the strand in the felt so i went back to traditional and all was good, i never had this problem in prior years so not sure if it was a bad batch. Scotty M