Key specifications include material composition, elasticity, and toe-seam construction. For premium markets, look for a blend of combed cotton (75-80%), nylon, and spandex for breathability and shape retention. The hand-linked toe seam (seamless) is a critical quality indicator for high-end Tabi socks, as it prevents irritation between the toes. Additionally, check the colorfastness rating (should be Grade 4 or higher) to ensure the traditional deep dyes (like indigo) do not bleed during washing.