Replacement foam for Shure 55SH or Super 55. Can also recommend using it to double the existing foam to get rid of some more of the plosives, which can be quite troublesome with these microphones, especially the 55SH. Thin strips of double-sided tape at the edges is an easy way of keeping it in place when doubling. If you're just replacing the existing foam that shouldn't be needed, though, as it sits right in.