Jiffy plastic tray of peat pellet contains 72-36mm pellets. Each one contains weed-free professional-grade canadian sphagnum peat. Add water and the Jiffy-7 peat pellet quickly swells to 7x its original size to become a self contained pot with its own perfect medium for starting seeds. Seeds are nurtured within the pellet to germinate faster into young seedlings. Roots emerge easily through the porous walls of the pellet as a result of the enhanced air circulation created by the unique design and characteristics of the Jiffy-7 peat pellet. The superior root development then assures stronger, healthier plants for transplanting.