Even when an item is a perennial, there are subtle shifts in material, proportion and silhouette that move the piece forward and speak of the “now”. Such is the case with this season’s trench coat. The newest must-have versions are boxy, with a straight, waistless shape. Firm fabrics or smooth leathers uphold the rectangular silhouette, and bellows pockets or flat-flaps echo the squared-off aesthetic. Sleeveless styles offer lots of options for easy layering. Most of the boxy trenches on the runways are minimalist, but Prada decorated the extended shoulders and flaps with an array of cabochons and colorful paillettes.