This study formulated a matching model for remanufactured products and users within Product Service Systems (PSS) to promote the circular economy. In remanufacturing, used parts exhibit varying levels of degradation. This degradation affects both user satisfaction and the sustainability of PSS models. By applying matching theory, we developed a one-to-many matching framework incorporating user preferences and the condition of used parts. The model characterises key allocation properties based on stability and fairness. Numerical simulations revealed that the probability of achieving stable and fair allocations was remarkably low when used parts combinations were randomly determined. These findings highlight the need for strategic decision making in assembling remanufactured products and allocating them to users. By addressing the inherent challenges in matching used parts, this study provides theoretical and practical insights for optimising remanufacturing-based PSS. These results underscore the importance of carefully designing allocation mechanisms to enhance sustainability and operational efficiency in circular economy practices.