A long sleeve bodysuit adds coverage without the bulk of an actual layer. It works under slip dresses, sheer fabrics, and anything that needs a smooth base underneath. The sleeves need to be fitted enough that they do not bunch under fitted clothing but not so tight that they restrict movement. The length matters too. Too short and you get that awkward half-inch of exposed torso. Too long and you are folding the cuffs. These bodysuits work specifically because the proportions are exactly right for their actual purpose. They sit under your clothes and do their job without becoming a visible part of the outfit itself. This is function that works.