More Details Milly Mackenzie Strapless Sweetheart Cocktail Dress Details Milly "Mackenzie" cocktail dress in technical stretch knit. Tied bow detail at bust and waist. Strapless, sweetheart neckline. Open keyhole on bodice. Fitted silhouette. Vented hem. Ruched back zip. Polyester/spandex. Lining: polyester. Made in USA of imported material.