Instruction: Output yes if the supporting document can answer the given question. Otherwise, output no.

Input:
Question: cage size??? is this the medium or the short cage?? cuz i need the medium.
Document: I replaced my (short cage) Rival rear derailleur with this one to increase the maximum rear cog size of my cassette. Previously, with the standard rear derailleur, I was limited to a 28t cassette (e.g., 12-28).
My new setup is compact crankset with 12-30T cassette. To support this cassette, I had to replace the stock short cage with this medium cage. It worked as intended. it covers large range from 12-30T and it should be able to support larger sprockets if I ever needed one.
I ordered this to replace my damaged Rival derailleur. My understanding is that my old derailleur was a medium cage. From pulley center to center was ~56mm.My local bike shop had in stock the long cage or WiFli version. The extra length would have required I lengthen/replace the chain.The version from Amazon sold as "medium cage" was the longer WiFli version. I returned it instead sourcing the correct size from another less local shop.Nothing functional wrong with it, I've been happy with Rival.
I'm running the short cage with a Shimano 12-27 cassett and an Ultegra chain. Shifting is very quick. Installation required a half turn of the high limit screw but no other issues.
I've installed SRAM Rival medium cage derailleurs on three of my recumbents in conjunction with SRAM trigger and bar end shifters, and SRAM 11-32 cassettes, Once they are dialed in the Rival derailleurs shift perfectly and retain their settings.
I switched from the small cage to the medium cage Rival rear derailleur because I wanted to try a 12-32 for the hills. I have found that it works great with the 12-32, the 12-28, and the 11-25. Having the ability to go to a 30 or 32 for hills over 10% has been a big help with keeping my cadence up to a reasonable level.
The best bang for buck performance derailleur SRAM has ever made. I have all Apex, Rival (which are identical excepts 12 or so grams in weight. I also have Force and Red, and I can see no appreciable reason to upgrade past Rival as they all four perform the same at SRAM!
If you're comfortable adjusting your rear derailleur, swapping this one in should be no trouble. I needed some hand-holding, though.Also, note that this is not the 11-speed rear derailleur.
I have this derraileur with rival shifters on my scattantte R670. They are as fast as ultegra but ship and ligth. I love the way it change gears. I do recomend sram products.
Great price for a solid product. I have had no issues with this derailleur at all. Sure, there are lighter models, but this is perfect for a non-racer such as myself.
Answer: no