A long sleeve bodysuit solves the problem of tucking in sleeves that want to ride up or bunch under fitted clothes. The sleeves add coverage and warmth while still being thin enough to layer under sweaters and blazers without adding bulk. These work beautifully under slip dresses, sheer fabrics, or any time you need an extra layer that stays exactly where you put it. The construction needs to be smooth and fitted through the arm so the sleeve does not create a line under a tight sweater. Look for versions in stretchy cotton blends or lightweight merino that move with you instead of against you. These are the layering bodysuits that become non-negotiable once you realize how much they actually solve.