Square D™ Load Center Surge Protective Devices (SPDs) are plug-in units designed for fast and straightforward installation. The surge suppressors use two pole spaces in a Load center. SPD are single phase and are rated for use in an indoor or outdoor enclosure. Ideal for residential and light commercial use, these SPDs provide a dependable first layer of surge protection. This is a plug on neutral surge protective device for Homeline load centers. It is designed to protect electrical service and major household appliances, excluding electronic devices. Designed for 3 wire 120/240 VAC single phase systems. Securing up to 50kA surge current per phase. This surge protection device is UL Listed.