Micro-train coupler help

[MercerMike]

Hello all.....Need a little help, Just broke the coupler off of my hopper and I am confused on what kind it is. The car itself is a Micro-trains #09900020, SAL Evans hopper, I looked on tag and they say it has Barber Roller Bearing trucks, now, here is where I get confused, went to Micro-trains site and I found 3 lenghts of couplers for this truck, how do I know if it is the short, medium or long extensions? What is the difference other than the length?
What is meant by extension. Obviously, I am new to n scale trains, but I am learning, need a little guidance..As always, thanks to all.

 

[MRLdave]

The truck is the same regardless of length. The length is a measure of how far the coupler face is from the bolster pin hole. If you don't get the right length the coupler either will stick out too far, or worse, not stick out enough from under the car. If you buy from a local shop take the car and they should be able to match it up. My guess would be the medium length, but it's only a guess.

 

[peteski]

Mike,
first of all, did you break off the entire coupler pocket from the truck or only the coupler's head broke off? If it is only the head then you can easily replace it with another one from any other Micro-Trains truck.

As far as the extension goes, that describes how far the coupler box is located away from the truck's center.

If you need specific part numbers, go to http://micro-trains.com/pl-NTrucks.php

For all the dimensions see http://www.nscalesupply.com/mtl/mtl-nscaletrucks.html
or http://micro-trains.com/Truck%20diagrams.pdf