Guild Wars 2

What can I use in the upgrade slot, tried gems, etc. nothing seems to work?

The level 80 jewels don’t work, because the backpack is only level 78 equipment. But the next lower jewel level works and the end result is still a bit better than the backpieces from Orr karma vendors and only a little bit worse than the ascended backpieces.

use a rare from this section http://wiki.guildwars2.com/wiki/Jeweler/Adept_recipes#Jewels. They say “equip” is 80, but when you click their individual page, they say 65 and its what I use in my back pieces too, so not sure what the “80” is about. for instance http://wiki.guildwars2.com/wiki/Embellished_Brilliant_Ruby_Jewel

Using T5 RARE JEWEL generates stat numbers that are slightly superior to any other EXOTIC back item you can buy.