Super Sprouter? Root Raft? replacement plugs make reloading your Root Raft? simple. Just clean your existing tray and insert, refill the floating insert tray, add water to your 10 x 20 inch tray and your good to grow. These plugs are specially sized for the Root Raft? Floating Plug Tray. They are custom blended and custom sized grow plugs. Mother Earth? BioChar added to this exclusive formulation.