https://morelectricheating.com/products/MANUFACTURERS/API/LOCKNDRY.aspx
LockNDry Indoor/Outdoor Power Supply Cord, 25 or 50 Feet
The revolutionary LOCKNDRY outdoor/indoor detachable power supply cord provides a weather-resistant seal while keeping the connection firmly secured. The specially designed plug on the LOCKNDRY cord fits any standard outlet, but when mated with a LOCKNDRY compatible power cord, the large black nut pulls the plug tight against the gasket to form a water-resistant seal. The red nut then locks everything in place and prevents cord separation. The LOCKNDRY is great as an all-purpose extension cord, too. 16 gauge, 13 Amp Rating, 25 or 50-foot cord. One year warranty.
• Secure water-resistant electrical connection
• General-use extension cord
• Indoor/outdoor
• Securely locks connection together