The interest in customization has increased due to globalization, and globalization makes competing on price more difficult if access to low-cost production is unavailable. Customization usually implies the creation of variants, where the final products are customized in form, place and/or time. However, the relation between customization and variants is unclear; therefore, the purpose of this study is to analyze customization in terms of form, place and time, as well as relate it to product proliferation (i.e., variant creation). Here, a time perspective is used, creating a clear relation to flow thinking. Using flow thinking and the two strategic decoupling points related to flow driver (customer order decoupling point) and flow differentiation (customer adaptation decoupling point) provides a better understanding of what, where and when customization can be applied.