Who makes the store brands you see at your local supermarket? Neither retailers nor big-brand manufacturers are anxious to reveal that information, and you won't find any clues on product labels.

Of the thousands of manufacturers of store brands, many are national-brand companies. That doesn't mean that national brands simply slap a different label on products that are rolling off the same assembly line: They sometimes manufacture a different type of product to be sold as a store brand, and even if it's the same type, they make it to the store's own specifications, which could mean a change in ingredients or quality.

What's more, suppliers can change any time: The company that made your store's chocolate-chip cookies last week might have been replaced by another this week.

Still, trying store brands carries little risk - most offer a money-back refund if you're dissatisfied - and the rewards can be considerable.

Peter Berlinski, editor of Private Label magazine, estimates that consumers can generally expect 15 percent to 20 percent average savings across all categories on store brands vs. national brands sold at supermarkets; 25 percent to 30 percent at drugstores; and as much as 50 percent at mass-merchandise stores.

If you're thinking about buying more store brands, here's the info you need to make savvy choices: