[CMcAllister]

How violently the car leaves and how hard the car gets on the bars, will determine the parts, pieces and design of the bars.

Does it need and use the bars? Or are they a "just in case" safety device?

Sprung or unsprung? Stick guys have always wanted sprung. Especially if they are on the short side.

Length? This is often a function of how close to the backdoor the car is in the trailer and if you are willing to install and remove them every time you load the car.

Material size? Diameter, wall thickness.

Budget?

You may end up sourcing parts and pieces from a few different places to get the exact configuration you desire.