1/2" diameter rubber head nails/cabinet bumpers for use on piano cabinets.  Head is about 7/32" tall (just under 1/4").  Most often used to protect cabinet surfaces that would otherwise touch and mar each other. Found on the keyslip (strip of wood across front of piano just under the key fronts), fallboard/key cover and occasionally the cheekblocks.  Also used under bench lids and piano top lids.  Also available in black and off white in my eBay store, also available in 1 smaller size and 1 larger size.