There are two supported mechanisms for displaying subitems in an item.

The scenario is that you might have items like a T-Shirt that comes in different sizes and colors. You can specify these in one of two ways:

• Custom Fields for Item Display Pages
  Using a special syntax for fields on a form you can capture custom information from users and store this content automatically into the ExtraText field of the lineitem. Examples: Name of attendees for a conference, capturing special meal requirements for attendees. It works great for any additional inputs that don't require a separate item sku.

• SubItem SKU support
  If you have physical sub selections and require separate skus for each of the items, there's full subitem support. With this mechanism you can specify a master item, display and select one of its subitems. Two different mechanisms for displaying and selecting subitems is available. The process is managed by marking subitems with a parent Sku.