Mondi Propagation Inserts 55-01 makes pellet expansion convenient and clean with even spacing and airflow for hassle free propagation. 55 propagation pellets fit snugly while maintaining excellent drainage through the large size holes. Thick plastic and UV protection for durability and long life. Grodan 1.5" rockwool cubes also fit snugly in these trays for easy cloning. The trays are made to fit cleanly inside Mondi propagation trays (plain black or premium).