When sourcing nylon stockings, the Denier (D) count is the primary indicator of thickness and opacity; lower denier (5D-20D) is sheer, while higher denier (40D+) is more durable. Look for a blend of Nylon and Spandex (Elastane), typically a 15-20% Spandex ratio, to ensure optimal elasticity and shape retention. High-quality stockings should feature reinforced toes and crotch areas to prevent 'runs' or ladders, and a double-covered yarn technique which significantly increases the lifespan of the garment compared to single-covered alternatives.