In order to contribute to engineering for QOL, dualism of universal design (UD) and orphan products (OP) is discussed. UD is for larger market size without adaptation, and OP is for smaller market size with extensive adaptation. In this model of assistive products (AP), AP is in a spectrum of UD and OP at both extremes. Definitions of AP by ISO and by ICF are discussed and the difference is illustrated using this model. The position of AP in the spectrum shows expected market size and degree of necessary adaptation. R&D aspects of AP are also discussed. Technology transfer from mainstream is beneficial to AP. A hypothesis is presented that AP tend to move towards UD extreme on the spectrum, if it is relevant to environment.