Quality function deployment (QFD) is a successful product design tool for analyzing customer demands. Recently, researchers have combined QFD and grey system theory for solving small size, uncertain and incomplete data problems. However, some problems, such as single grey values, competitive analysis and prototype product selections, require further investigation. To resolve these issues, this study integrates interval grey numbers, QFD and TOPSIS techniques to develop a grey product design and selection (GPDS) method. GPDS can help product developers identify important engineering characteristics, perform a competitive analysis and select the best prototype product(s) under a small size and uncertain data environment. A real-world case study (paper facial mask) is offered to explain the research process of the GPDS method. The case results indicate that GPDS helps the case company identify important engineering characteristics, understand the intended market position of a product and select the best prototype product.