Motor post/coupler

After reading a description for a 393 motor, two terms stuck out, motor post and motor coupler. I was wondering if anybody could enlighten me on what these are specifically, thank you.

They’re these:
http://www.vexrobotics.com/media/catalog/product/cache/91/image/5e06319eda06f020e43594a9c230972d/f/i/file_61_5.jpg

The idea is that they are the same size as the old VEX clutches that you had to use with the weaker previous motors, so you could simply replace the clutch with this instead of having to install a longer axle. I haven’t seen them used much (and never have myself), as most people just push the shaft directly into the motor, but sometimes they’re helpful for things like making a motor easier to remove and replace.

My team has found that in some applications, use of the motor couplers (I’ve also heard them referred to as “clutch replacements” means that the length of the shaft is more in line with the dimensions of whatever it is we’re building. This can be particularly useful, as it means we do a lot less cutting of custom-length shafts from our stock of 12" shafts, something we found ourselves doing alarmingly often before we started using the motor couplers.