Super Sprouter? 50 cell Root Star? tray insert is custom designed to properly support the Perfect Plugs while directing the roots down through its star pattern design. The patent pending design also allows partial root pruning to strengthen the directed roots. Fits snugly into Super Sprouter? 10 x 20 in propagation trays. This Root Star? insert is very durable at 2 mil thickness. Individually marked with a UPC label for retail use.