Silvercup is not longer made by the Nelsons. It's owned by Skretting now.
http://www.skretting.us/Internet/SkrettingUSA/webinternet.nsf/wprId/2607D87D2C89FADBC1257999003AA253!OpenDocument
Here's a web page with feeds you're likely choosing from. They offer both sinking and floating. All different names for the different feeds than we've gotten used to.
http://www.skretting.us/internet/SkrettingUSA/webinternet.nsf/wprid/C377F4B9D0D7A7E388257CD3007037DD/$file/SkrettingUSA%20Warm%20&%20Cool%20water%20Diets%202014%20for%20website.pdf