We have multiple hopper trailers that have electric tarps and traps.  I have found at least 3 different styles of plugs for the 12v power cord that are needed to operate them.  They come in either a horizontal or vertical orientation of the two pins...plus we just realized that there are two sizes of pins in the plugs with a vertical alignment.  I want to get all of ours to the same size so that we can swap trailers between trucks if necessary.

What is the reason for the different options?  Is there a certain style that is the standard?  We have moved towards the plugs with vertical alignment in the past...but just realized that we have both types of pin sizes of the vertical ones.  It looks like we have roughly a similar amount of both sizes, so that doesn't weight in the decision too much.  

I would prefer to move towards the style that will more likely be the standard down the road (or maybe already is) if possible.

Here are the different styles that I have found:







Thanks for any advice.

NK