There are distinct differences in the active ingredients and percentages between the Sprint 138 Chelated Iron and the Sprint 330 Chelated Iron. You can use the compare tool on our site, or follow THIS LINK to see them compared side by side. The Sprint 330 contains 7% Nitrogen and 10% Iron, whereas the Sprint 138 contains 4% Nitrogen and 6% Iron. The higher percentages will give a deeper green and more growth to the lawn than the lower percentages.
Typically chelated iron like Sprint 330 Chelated Iron 10%