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

Input:
Question: Is this a single item or is it a set?
Document: Works perfectly. replaced an old twist grip shifter and it works so much better. Highly recommend it as an upgrade.
Upgraded my MTB from wrist shift to these AMAZING shimano rapid shifters. I had the opportunity to ride a 2010 Specialized S-Works Stuntjumper on a demo day and I can say that the Acera shifters change gears almost as quickly as a $7000 bike, that is if your bike has been adjusted and that the drive train isn't heavily worn. I have crashed numerous times (two of which I rolled over onto the handle bars) and the shifters still perform like the day I bought them.
This was an upgrade to the one that came from the factory. It works, easy to install, and it looks better.
This was a replacement for an Acera shifter I had. It works but won't shift all the gears no matter how much adjusting I make. At least I get 6 of the 7 gears, so it's not too bad.
These things are great ! In pics they look like plastic crap, but make no mistake , they are all metal, look GREAT & work fantastic ! As others have stated ,they are gummed up when you first get them, but I just sprayed some WD 40 in em & now they click gear to gear perfect . Every shift is dead on.Up or down. These shifters  DO NOT COME WITH BRAKE CABLES. They do come with shift cables & housing.
It's a shifter/brake and does just that.The GOOD part is they are compatible for V brakes OR older canti's with an adjustment. 4 finger version only.
Highly recommend them. EDIT : After a while they started to stick again. Took them apart, cleaned with WD then oiled them. Seem to be working a little better, so I complained to GREEN CANYON OUTFITTERS & THEY SENT ME A BRAND NEW SET! Even though they were 3 months old! I will be buying ALL my bike parts from GREEN CANYON OUTFITTERS from now on ! GREAT CUSTOMER SERVICE !
Good value for replacing original equipment. Arrived as advertised good fit for my hands. Too bad i need to sell the bike
Answer: no