Burpee 72 Count Coir Seed Starting Pellet 22.5mm Burpee Super Growing Pellets are designed for Burpee Ultimate and Eco-Friendly seed Kits and will expand to fill most 100 or 72 count trays Our unique coconut coir is specially formulated to get your seeds off to the best start possible Holds more water with better air circulation than ordinary peat pellets Refill for Burpee 72 cell ultimate seed starting kit Pellets measure 3/4" diameter before expansion