This article presents a study of the design history of the snowsuit as a product type and explores the constitutive factors in its development. To shed light on the snowsuit as a designed object, the study draws on Actor Network Theory (ANT), particularly work linking ANT to design. In order to do this, the study focuses on the Finnish company Reima, which has been a leading producer of children's wear in the Nordic region since the 1960s. The article traces the development of the one-piece snowsuit from a marginal product type, whose use was advised against because it was seen as hindering children's freedom of movement, to the ubiquitous position it holds in Nordic pre-school children's wardrobe today. Innovations in textile technology play a prominent role in this development, as does the emergence of a new configuration of use, characterized by working mothers and institutionalized children, which has increased the demand for garments that are practical, robust and easy-care. The article argues that the snowsuit is essentially a technique for making children more 'suitable' for institutions and links the snowsuit to a broader movement towards the rationalisation of family life in the welfare state.