Professional packing companies call it "void fill." That is the empty space left in your shipping box that needs to be filled to keep the product from moving about during shipping. There are many items that can be used - bubble wrap, old newspaper, paper grocery bags, styro peanuts, and so forth.
But what about the common inflatable balloon, the one your kids like to play with.
Here are some advantages to using inflatable balloons:
1. They are easy to find and buy. Dollar stores, grocery stores, ebay, big box retailers, toy stores, and party stores. Small bags of balloons can be purchased for as little as $1.
2. They weigh almost nothing. On my digital postal scale a large balloon weighed .2 ounce.
3. They are colorful. Your customer opens the shipping box to a joyful collection of colorful balloons.
4. They take up a lot of empty space. Wedge them in and they will hold your product safely and securely.
5. Sizes are available from small to large, and even the elongated versions, that will fit almost any need. The balloons that are helium-safe are studier.
6. Use a bicycle air pump if necessary. Small balloons can be especially hard to inflate.
One word of caution:
If your customer opens the box with a sharp blade, the balloons could explode. If that danger exists, include a note on the top of the box informing the customer that "inflatable packing material is used - open carefully." Sometimes I place a piece of cardboard over the balloons to avoid that danger.
Using colorful inflatable balloons is a creative way to fill that empty space in your shipping box. I have found from ebay feedback that customers like it.