By studying fashion market, this research aims to analyze legitimacy issues existing between two market categories: the primary market of mainstream fashion and the secondary market of plus size fashion. Through the lens of the Consumer Culture Theory (CCT), we observe dynamics based on practices and material devices which create symbolic, physical and social (in)visibility of market categories. Our doctoral work examines new approaches to market dynamics. The first contribution highlights four types of dynamics (attractiveness, opposition, circular and systemic dynamics), which allow to reinforce the mainstream fashion market category legitimacy at the expense of the plus size fashion market category. The second contribution explains that categorization is not a question of social representations, discourses or interactions only, but involves material devices too. Materiality appears as a visibility and invisibility device. Finally, we bring forward the social visibility issues. Behind physical invisibility (not to be seen, to be hidden…) there is social invisibility (not to socially exist). Plus size women feel then illegitimate and excluded from the fashion market.