Review on Leisure Cords Trailer Dogbone Adapter: 15 Amp Male to 30 Amp Female Locking Connector with LED Power Indicator - Enhanced Convenience for RV Power Connections by Carl Watkins

There are several versions of this device but this is the best. Having 110 pins on an extension is very, VERY important for these devices. Whether you're using it for an RV, a washer/dryer, or perhaps a home data center rack, the cables you'll be connecting to it are very heavy and tend to be very long, so a 30 amp outlet is a must naturally hanging face down on the wall by gravity. Attempting to use one of the other solutions and plugging it directly into a 90° outlet didn't work and kept falling out.