Progressive Industries Smart Surge Protectors (SSP) are portable RV surge protectors with the added benefit of a built-in polarity tester. The built-in surge indicator notes the condition of the surge protector. Additionally, the polarity tester (dual line for 50A) checks the status of the power source prior to use. Sleek, compact, portable design makes it easy to use and store. Designed for outdoor use. No installation required.