Rear Derailleur - need help!

Hi,

I want to buy a new rear derailleur, but the Sram X.9 as 3 sizes, long, medium and small cage.

I have one Sram PG990 32T cassette on the back.


My chainset is a XT, 175mm (26T.36T.48T).

What size should I buy, long, medium or small cage?



Thanks,
Miguel

Long I think.
It generally goes
3 rings up front = long
2 up front = medium
1 up front = short

Medium or Long would be fine.

Thanks a Million!

go long esp. with a 48 triple