Which coupler to use?

[mkgr]

I have a Bachmann On30 set, and I need to replace several couplers.  How do I know which to order, i.e. center, over, under-shank; short, medium, long shaft?  Thanks

[the Bach-man]

Dear MK,
Most are medium length. Check similar cars to determine which shank position.
Have fun!
the Bach-man

[mkgr]

Thanks but how do I know what I'm looking at?  That is, what is the shank?  Is it the piece of steel that meets the block-like thing?  So if it's on top, that's called a "over shank" or what?  Is there a diagram somewhere that explicitly defines this?  I assume that all the couplers have to be the same type in order to mate properly.

[GN.2-6-8-0]

Take a look at www.kadee.com 

You'll find all the information you'll need.

[mkgr]

Excellent!  Thanks!