I have 3 SRAM XO rear mechs to sell...
1. Original production with carbon effect knuckle, upgraded to a blackbox full carbon cage (short) a few years ago. Pretty scuffed up looking as has been used but it still smooth to shift with no rattling. Jockey wheels are used but spin ok. £40posted ono
2. Slightly newer version with grey knuckle, has a medium blackbox full carbon cage. Good condition with only a few marks and some slight scuffing. Again, jockey wheels are used but spin ok. £50posted ono
3. Spares or repair, got bent when bike was knocked over, think the parallelogram is twisted? cage is a long version aluminium and is perfectly straight (didnt take impact), no jockey wheels. £15 ono