Medicap FE FE1210 Systemic Iron Tree Implant, Pack of 10 Systemic iron tree implants Useful in trees where iron deficiencies are difficult to control by foliage or soil feeding Trees most susceptible to iron deficiencies are pin oak, black locust, birch, pines, magnolia, dogwood, peach, pear, apple, etc Easy to install; 5 implants per pack 3/8-inch diameter implant