One stackable tray for use with the Worm Factory Standard model and Worm Factory 360. The Worm Factor composter uses worms to break down organic waste. Its compact design makes it perfect for use in any household. It is easy to recycle kitchen scraps and paper into nutrient-rich fertilizer for your plants. Managing the Worm Factory takes less than 15 minutes a week. Add worms and your organic waste to the bottom tray. Once that tray is filled add another. The worms migrate upward leaving their compost behind. It works year-round inside or outside. The finished compost can be used on any plants.