Super Sprouter� Root Raft� Refill 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 in tray and you're 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 is added to this exclusive formulation.