Product details list polyester as the material. Although the items are described as denim, the listing indicates they are a denim-style fabric made from polyester.
They feature a square neckline and a front button (button-down) closure.
The vests have a corset-inspired open/backless look with a smocked back panel; the smocking adds stretch and provides some adjustability for a better fit.
Follow the product care: machine wash, then line dry or lay flat to dry.
Product details explicitly list that there are no pockets.
A smocked/stretch back panel provides added elasticity, helping the vest fit snugly and comfortably across different body shapes.