Magento comes with a great demo catalog, and inspecting it can be a great way to get tips on how to set up your products in your store. However, you may want to think twice before following its example for setting up products that come in different sizes, such as clothing.

The demo catalog contains a Simple Product for every single size of a product you wish to sell. These products are not visible in the catalog, but are available as options on a Configurable Product in the catalog. Not only can this quickly bloat your back-end, but if you should decide to begin offering sizing options after the product is created, you'd have to scrap your product and begin again as a Configurable Product.

Fortunately, there's a much more streamline way of accomplishing this: Simply add Custom Options to your product. This option allows you to add options which carry their own SKU, and can even affect the price (eg +$3 for XXL). Here's how to do it:

Log into your admin panel and navigate to Catalog > Manage Products and click on a product to edit it.

Select the "Custom Options" tab from the left-side navigation and click on the orange "Add New Option" button that appears in the upper right corner of the main area.

Set a title (eg 'Size'), set Input Type to "Drop-down" and set as Required. Then click the orange "Add New Row" button below. Fill in the Title, SKU, and Sort Order for the first size, then click the "Add New Row" button again and repeat for the remaining sizes.

That's it! Now you can sell multiple sizes of your product on your Magento store in a single catalog entry!