Summerstep SMEC24 - Connectable 2 Foot Watertight Extension Cord 120-Volt - 12 Amp Max The Summerstep part number (SMEC24) 2-Foot connectable watertight extension cord can be used with our Commercial Snow-Melting Walkway Mats (WM24x60C, WM36x60C), Commercial Snow-Melting Stair Mats (SM11x36, SM11x48, SM11x60, SM11x72, SM11x84, SM11x96), and Commercial Snow-Melting Door Mats (DM24x36C, DM36x48C, DM48x60C). Each set of Summerstep Commercial / Industrial Snow-Melting Mats (up to 12 amps) requires one power unit to connect the system to an electrical outlet. Up to 12 amps can be connected on a single 6-foot Summerstep power unit. If your connected mats exceed 12 amps, you will have to split up the heated mats and add a second power unit to plug into a separate outlet.