Amazon: nema 3r box
50 Amp Generator Power Inlet Box, NEMA 3R Power Inlet Box, SS 2-50P, 125/250 Volt Generator Inlet Box, for 3 Prong Generator Cord, 12,500 Watts, Weatherproof, Outdoor Use, ETL Listed. 4.1 out of 5 stars 6. $49.00 $ 49. 00. Get it as soon as Tue, Jul 13. FREE Shipping by Amazon.