These are a nice mid-weight cotton one-piece.
I agree with the other reviewer, that these run long in the arms. The outfit fits perfectly everywhere, except for 2 inches that we roll up on each arm. Our son is 4 months old, but fits 6 month old clothes, in general. I purchased the 6-9 month size and they are perfect.
Sleeves are not a deal-breaker for me... I purchased these on sale and am very happy with the material and overall quality.
Extra plus is the cute design!