SUNPACK® Black 4-Cell Tray Insert Square SUNPACK® Injection Molded 4-Cell inserts are made from premium Food Grade, and BPA-Free plastic. 12 inserts fit into a standard 1020 (10in x 20in) tray. They feature side slots on all four sides for air prune technology. Air channels are added on each side to prevent root circling. Air pruned roots are shown to provide healthier and more vigorous growth.