Each box features slotted foam internally on the top and bottom lid, and unlike other boxes on the market, one external slotted foam sheet for easy drying, organizing or quick access while behind the oars. The thick durable foam features fly placement guides to easily identify where the slots are located. DIMENSIONS:Umpqua Magnum / 16.5" x 12" x 4.5"XLarge (Ultimate) / 13" x 10" x 3.5"Large (Baby) / 10" x 8" x 3" Fits Umpqua Boat Box foam sheets