Usually something of equal rarity and value. I traded one of mine to my regular trading partner for a bottle of town hall twisted Jim.
I traded a wooden hell for CFH x 5. I realize the wh probably could've gotten me some ultra rare bottle, but I have had the cfh and think it is the best BA beer I have ever had, so I was happy to get multiples of it. And I think the guy who I made the trade with (or perhaps him and his buddies?) we're excited to get to try the wh. I guess my point is, if you dont have something to trade straight up for cfh, maybe you have something worth more than a cfh that you could get multiple bottles for?