If you want a product to be available only for bundled offers, no problem! Within the RMS, find the product. From the Settings menu for that product, select Restrictions and then check the box next to Check if this item can only be sold as part of a bundle. This will prevent the product from appearing on your eComm site or within the CRS.
You’ll also notice that you have the option to restrict certain products to be available only within packages. These settings give you additional flexibility when creating bundles and promotions.