RDS Below Deck 20 Gallon Wedge Tank Special Order - Ships When Available. Contact customer service for more information on Special Order items. Dimensions 36 12 L x 19 H. Top 8 Wide, Bottom 6 Wide Side Corners are radius bent, not welded All tanks have 14 NPT pickup, 1 12 fill, and 12 vent fittings Add 3 to height for fittings Gasoline only. No return fitting for diesel fuel Above Deck Tanks have vented caps with guage units Below Deck Tanks have electrical sending units and removable vent plugs