Rusco SS1 Sun Shield The Rusco SS1 Sun Shield inhibits algae growth inside the Rusco water filter system cover, which can grow inside clear covers if sunlight is not stopped by a sun shield. The Rusco SS1 Sun Shieldonly works on 0.75" and 1" Rusco Spin-Down Filter Systems and Vu-Flow 1" Screen Filters. The Rusco SS1 Sun Shieldonly works on 0.75" and 1" Rusco Spin-Down Filter Systems and Vu-Flow 1" Screen Filters. If you have a 1.5" Spin-Down System or a 0.75", 1", or 1.5" Sediment Trapper System, you must use the Rusco SS1.5 Sun Shield.