Worm Factory Composter Extra Trays (Green) Set of 4 Separate trays to add to your Worm Bin Base. Made in US from recycled and food grade plastics Upgrade trays available to expand the 3, 4, or 5 tray models Each add a tray adds 3.5" to the height of the worm bin 5 year warranty on on materials and workmanship, Made in the USA