What is a Weight Distribution Hitch System? 
An optional system which can be added to most rear mounted trailer hitches. The system includes supplemental equipment such as spring bars, that work to distribute trailer tongue loads to the trailer axle(s) and the tow vehicle front axle.  Use of weight distribution system enhances handling and braking and in some cases increases the trailer towing capacity (only if the hitch has a weight distributing capacity from factory.)

*Note* For Weight Distribution Hitch System part breakdown, refer to What Are The Components In A Weight Distribution System

When is a Weight Distribution Hitch System needed?
When towing a trailer with a standard ballmount, all of the trailer's tongue weight is transfered to the tow vehicle. Having too much tongue weight in relation to gross trailer weight can cause the back end of the vehicle to lower and the front end of the vehicle to raise. This will cause you to loose braking traction, steering control, and increase trailer sway.

How to choose the right Weight Distribution Hitch System?
A weight distribution hitch will have two ratings, the gross trailer weight (GTW) and tongue weight (TW). GTW refers to a combination of the weight of the trailer and all of its contents. TW is the downward force excerted on a rear mounted trailer hitch when the trailer is attached.  With a properly loaded trailer, the tongue weight is approximately 10% of the gross trailer weight.

There are many styles of weight distribution systems. When choosing a weight distribution system you should consider the following:

1. Round or Trunnion Bar Style (refer to differences in Round vs Trunnion bars)
2. Tongue weight and if you need sway control (refer to What Is Tongue Weight?)
3. Required towing capacity (refer to trailer specs and vehicle towing capacity)
4. Preferred Brand (this may come down to budget)