Stack Height depends on the model, but typically the stack height at the center where the spindle would be is about 6.5-7.5mm unloaded. That will change when a foot is in the shoe and the middle board is compressed. We recommend working directly with a bike fitter when setting up any new pair of cycling shoes. A bike fitter will be able to assist you with cleat alignment as well as setting the saddle height and position to address any stack height concerns. Working with a fitter will allow you to optimize your performance and get the best return with your new shoes.