Seedling tray is made of plastic material in various hole size options. Type #1 - approx. 2.5cm x 4cm depth (200 holes) Type #2 - approx. 3.5cm x 4cm depth (105 holes) Type #3 - approx. 3.8cm x 4cm depth (72 holes) Type #4 - approx. 4.5cm x 4cm depth (50 holes)