With Variant Blocks in Simulink, you can represent all design alternatives of a system in a single model. Each design choice is incorporated into the model as a variant choice in a single layer or a separate hierarchy. Such models have a fixed common structure and a finite set of variant choices that are activated or deactivated depending on the variant controls you select. For information on variant controls, see Introduction to Variant Controls. The variant activation time determines when to activate the choices and whether to include only the active choice or both active and inactive choices in generated code. For information on activation time, see Activate Variant During Different Stages of Simulation and Code Generation Workflow.