In the traditional new product development process, manufacturers first explore user needs and then develop responsive products. Developing an accurate understanding of a user need is not simple or fast or cheap, however. As a result, the traditional approach is coming under increasing strain as user needs change more rapidly, and as firms increasingly seek to serve "markets of one." Toolkits for user innovation is an emerging alternative approach in which manufacturers actually abandon the attempt to understand user needs in detail in favor of transferring need-related aspects of product and service development to users. Experience in fields where the toolkit approach has been pioneered show custom products being developed much more quickly and at a lower cost. In this paper we explore toolkits for user innovation and explain why and how they work.