Tomato fruit set products are hormonal products designed to substitute for natural pollination. These products work best when tomatoes are failing to set because of cool temperatures. Tomatoes that set after use of these products will be puffy and have less seed than fruit resulting from natural pollination. As with all chemicals, you must follow the label directions when applying hormonal products. For more information on growing tomatoes and other garden crops, visit the eXtension website: Vegetables.