Mass customization is a business strategy that aims at satisfying individual customer needs and provides them a large product mix. To achieve this goal, it is necessary to manage the product life cycle activities especially the volume and variety of products which have to be easily customizable. Designing modular products increases the possibility of obtaining customizable products. The modular design consists of breaking down a product into more or less independent sub-elements called modules. This paper focuses on setting up a Genetic-based automatic product variants generator. The product used as the testbed is a LEGO plane composed of bricks. Different operators are used for selection, crossover and mutation of genes. Each final plane assembly is qualified based on some criteria to respect pre-defined constraints. The obtained final assemblies are discussed at the end of the paper to highlights future challenges.