The Under Current® Expansion Kits allow you to easily expand your Under Current® system. All Expansion Kits include Multi Mod Growth Modules with Drain Out Kit, CCH2O Joints with UC Spin Tight Bulkheads, CCH2O Lid 5.5”, CCH2O Net Pot 5.5”, Aeration Manifold fittings, Aeration Hose Leads and Sintered Airstones. For all 13-gallon, 30" spacing Under Current Systems. *For Multi Mod systems ONLY.