Our Seedling Tray Inserts are durable and reusable and will stay with you through many growing seasons. Available in 50 cell, 72 cell, and 98 cell packs, these inserts will fit into all our 10 x 20 trays. Our Seedling Tray Inserts are durable and reusable and will stay with you through many growing seasons. Available in 50 cell, 72 cell, and 98 cell packs, these inserts will fit into all our 10 x 20 trays.