The extension cord comes in 10, 25, 50, 75, and 100 feet in length.  It is a NEMA TT-30P to a NEMA L5-30R.  This 3-prong extension cord is heavy-duty and is used to get 125-volt power from a generator or campground power pedestal.  It can be used for RVs, food trucks, and even emergency power.  The cord is flexible and durable as well as weather and water-resistant.
 
NEMA L5-30R, 30 Amp, 125-Volt, 3-prong locking female receptacle
Soow 10/3, 600-Volt rubber jacket with a 30 Amp copper wire
NEMA TT-30P to NEMA L5-30R
Stays flexible in cold weather
NEMA TT-30P, 30 Amp, 125-Volt, RV/trailer male plug