Sunlight Inlet Louvers play a critical role in eliminating sunlight penetration on cooling tower basin water. EVAPCO WST inlet louvers stop sunlight penetration on basin water and assist in minimizing biological growth. EVAPCO WST inlet louvers are a much needed upgrade to the original AQUA-COOL ME100 inlet louvers which allowed sunlight penetration and water splash out. MSS, MEC, MFC units manufactured post 2010 use WST inlet louvers - it is highly recommended that units manufactured before 2010 have WST inlet louvers retrofit to enhance compliance with Australian standard AS3666.1 Clause 4.6