Grow1 Propagation Domes are made of heavy duty, clear plastic to improve seed germination and success rates of cuttings. These sturdy 12″ propagation domes allow light in while keeping moisture levels high and constant. Propagation domes will also retain heat supplied to the root zone making them great for seed starting and root cuttings! Grow1 Propagation Domes will fit most 10” x 20” propagation trays available on the market.