These are great base layer shirts! They The wool silk cambo wicks water away from the skin and keeps my baby warm if she spits milk on herself.

I love the material of this onesie, it is so soft and has a nice stretch. I got the 74/80 size for our then 11 month old, ~20lbs. It fit her perfectly (with a cloth diaper too), but not much room to grow, so I would say true to size. My issue with it is the shape of the snap area around the legs. It is very tight, so I had to un-snap the two side snaps and only keep the middle one snapped to keep it from digging into her thighs. I don't know how her thigh thickness is compared to others, but I think she's pretty average, not super chunky. Also, the snaps themselves are very small and not the easiest to snap (my husband and I agreed on this, and we are dextrous 30/32 year olds!). I wish I was handy enough to cut and adjust the shape! Planning to get the long sleeve shirt from Living Crafts.