Current Culture 1-Site Multi-Mod Expansion Kit for Under Current with Four-Site Lid (4 x 5.5" Net Pots)1 Site Expansion Kit Is Great For Replacing a Single 8 Gallon Growth Module for Under Current! All Expansion Kits Now Include: Multi Mod Growth Module, Aeration Manifold Fittings, and Air Hose Whips. NOTE: This multi mod expansion kit is designed to be used to expand the new 2019 multi mod under current systems. This expansion kit will NOT work with the classic systems. If you are looking to expand an old classic under current systems, please call us