My students really liked these models. They literally said 'Oh, I see!'. We had gone over these processes several ways before I used the model to allow each student a chance to work through all the concepts on their own. I just wish I could afford more than 1 set, so that my students could work through them rather than watching me run through the steps. The supplemental worksheets on their website are also great review, but all of the answers are available online - I just assigned sections of the worksheet during class.