I was in Costco picking up some of the merino socks (great deal, we'll see how they wear) among other things and saw some baselayers – paradox brand that were a merino blend. They seem similar to the merino blend bottoms and tops at Target (their C9 Champion brand) – both of which have a small amount of merino in them. I think the Costco ones had maybe 11% and the Target ones similar (might have been slightly higher but I don't think more than 15%).
Anyway – while good prices I've been pretty happy with the C9 100% synthetic base bottoms I have to sleep in – and was wondering if the slight wool content really makes a difference or do you need to go to 50% or more to appreciably gain benefits of the wool?

