100 precut upright piano hammer butt felt squares, thin (about 0.110"). 5/16"x3/8". Use on spinets, consoles, studios and uprights and I've even seen some use for felt this size on older grands too. A click upon releasing the key (on verticals) can sometimes be attributed to a missing butt felt.  With a flashlight look at the hammerbutt, just behind the jack and verify that the felt is intact and in good shape (see photos).

I've been a piano technician specializing in restoration for over 30 years - if you have a question about this item I'm glad to help before or after the sale.  My contact info is included in each shipment and you can also reach me through eBay.