Listings describe active onesies as using high-stretch nylon–spandex blends that offer comfortable elasticity and a sleek, flattering shape. Many styles use double-layering and soft, breathable construction to improve fit and comfort.
Common necklines include crew, square and mock-turtleneck styles. Sleeve options range from long sleeve and short sleeve to sleeveless across the available designs.
Several styles use double-layer or double-lined construction to reduce transparency and add coverage, often combined with breathable, lightweight fabrics.
Some styles use a thong design or crotch closures and double-lined construction. Descriptions note these approaches help prevent visible panty lines and keep the fit smooth without riding up.
Mesh and sheer panels add visual dimension and create a slightly sheer, fitted look. Some mesh short-sleeve styles are noted to run tight while still providing a fitted silhouette.