Make the most of your mower with an Agri-Fab spike aerator. Spike aerators use a series of rotating star-shaped tines that slice into the soil. This allows seed, fertilizer, water, air, light and nutrients to reach the grass roots. Aerating should be done when the lawn's moisture content is high. the 40 in. spike aerator provides up to 2.5 in. of aeration depth by adding up to 100 lbs. to the weight tray. When you aerate your lawn, you are opening up the soil surface to let grass roots get the air and moisture they need for healthy growth.