When it comes to product packaging, consumers tend to be “glass is half empty” types. At one time or another, nearly everyone has complained about opening a new bag or container, and finding that a good portion of the space inside is occupied by air. Sure, most products are sold by weight, but it still feels wrong to buy something and find out that the package isn’t filled to the top with the desired product.

Aside from disappointing customers after they’ve taken the product home, there’s a special situation that can hurt in-store sales, too. What am I referring to? The combination of a transparent package with a product that tends to settle during shipment, or a package that’s purposely too big to give it more visual presence in the store. In this situation, shoppers can immediately see if the contents seem skimpy by simply looking through the plastic, which can have a very real impact on sales.

The solution is quite simple: unless you feel really good about how much of the package your product normally takes up, then don’t include a see-through window. Otherwise, you’re putting yourself at a disadvantage compared to competing products that are sold in opaque containers, even when there’s just as much air in a competitor’s packaging.