The SunXCD rear derailleur is a long cage rear derailleur suitable for touring and road use. The long cage allows use of a wide-range cassette (11-34t max) and with a maximum capacity of 39t. Some good examples would be running something like -
The return spring is nice and strong, which is essential on a touring bike. There is a barrell adjuster for easy 'on-the-go' gear adjustments. Compatible with up to 10 speed (Shimano fit).
Note - I have used this mech with a 11-42t cassette with some success :)
I have decided to stock both versions of this mech, the original Microshift and the re-branded SunXCD version. As you can see, there is a significant price difference for the same product. The choice is yours.