NDC numbers are made up of several components. An 11-digital NDC number is broken down into three separate parts; the labeler code (which identifies the manufacturer), a product code, and package size. The 10-digit format eliminates the package size and count part and only includes the labeler code and product code. The length of an NDC number can vary depending on whether it is for an individual or multiple items, so make sure to double-check the format you need before using an NDC on your product labels.