4″ Site Plug for Aeroflo System Square Chamber Hydroponic Systems. When you need your system running and need to replace sites with new clones or simply aren’t using all available spaces. Use site plugs to cap off those sites and continue growing with the rest of your system. These plugs fit perfectly into the site and remove the chance for any water to escape or light exposure to your nutrient solution. Plugs also Protect grow chambers and nutrient solution from contamination by dust and debris. Keep your system running clean. We do not recommend using anything other than site plugs to cap unused sites as you run the risk of damaging the system components.