We got so many people asking how to know if a Shimano derailleur has a short cage or a long cage so we decided to write this quick and easy guide:

Basically all Shimano rear derailleur are available in Short or Long cage.
To know the difference is by looking at the last 2 or 3 letters in the Shimano code (most of the time parts are listed by their Shimano original parts reference number)
For example a dura-ace rear derailleur code is: RD-7800 it will be followed by the letters SS if it is a short cage or GS if it is Long cage model; looking at the full reference will be: RD-7800-SS or RD-7800-GS
It is the same for all the Shimano road type rear derailleur, they all either end by SS or by GS

Shimano MTB rear derailleurs  last letters will be GS or SGS, which stand for "Short cage" or SGS for long cage.
A XTR rear derailleur will be RD-M970-GS (for short cage) or RD-M970-SGS (for long cage)