Supplier-buyer exchanges are well addressed in literature except in the case of unknown objects. Sourcing Innovation, i.e. the process of finding external sources of innovation and then bringing those innovations into the firm should transform incoming unknown objects to ascribe them value. Technology Readiness Levels (TRL) have formalised the unknown in supplier-buyer exchanges in many industries for forty years but there is no evidence that they enable that transformation. We then use design theories, i.e. the Technology-Environment framework, to probe TRL through analysing ten cases combining documents analyses and longitudinal studies. We found that TRL avoid fixating on a low mature technology and are not an obstacle at genericity; however they fixate when the buyer waits a certain TRL prior exploring the new technology value. Finally TRL are unable to guide designers towards generativity notably because they embrace a definition of Environment focused on the prototyping method.