National Garden Wholesale Super Sprouter Quad Thick Propagation Tray with Holes, 10 Inch x 20-Inch These reusable trays are built tough for long lasting durability! They are injection molded, where most 10 x 20 trays are vacuum formed They are four times the thickness or regular 10 x 20 trays No need to use multiple trays to gain strength when one quad thick tray will do the trick