Techniques are described for describing and associating custom products. In an embodiment, a first attribute value that defines an attribute of a custom product is received from a user that is customizing the custom product. In response to receiving the first attribute value, a legal set of attribute values for a second attribute of the custom product or an accessory product may be determined. The legal set of attribute values identifies one or more attribute values of the second attribute of the custom product or accessory product that are compatible with the first attribute value. The legal set of attribute values may identify a continuous range of values where any value within the continuous range of values is compatible with the first attribute value. In an embodiment, the user may be limited to selecting accessory products having a legal attribute value.