Originally Posted by gbaglo
Do some more research and I think you'll find the "weight carrying hitch receiver" is Class II.
Class III is required a weight distributing hitch.
The hitch classes are just weight capacity ranges, so any hitch rated for 5000 pounds (or indeed anything more than 3500 pounds) of trailer is Class 3. Between 5,000 and 10,000 pound capacity makes it Class 4.
The now-ancient VESC V-5
standard defines weight distribution, but the current SAE J684
standard makes no reference to weight-distribution systems at all. A WD system could be used in any class, and a hitch can be any class without being required to allow WD. It is just normal practice in the North American towing equipment industry to make WD hardware only to fit 2" and larger receivers, and to use a 2" square receiver size for Class 3.
So in practical terms, you do need Class 3 or higher to use WD, but not all Class 3 receivers allow WD.