This product claims to be the best at eliminating, (not just covering up) all organic odors - including, but not limited to the Singer Featherweight Case. We believe it works very well for smelly cases, too! We've even tested it on odoriferous vehicles, shoes, pet smells, strong cooking odors, etc. It's even been tested in mortuaries! It can be sprayed, poured or wiped directly on the source of the odor. There are approximately 200 squirts per 1 oz. bottle, but it is highly concentrated and even a bad smelling case would only need a few squirts. For mild odors, one or two squirts will suffice, but for stronger, moderate smelling odors try 3-4 squirts. Close case lid and let sit for a couple hours. Repeat as necessary.