Fabletics black workout capris with back details. Motion365 Made by Fabletics.

From their website: Motion365® is our most versatile fabric, designed to give you all the sculpting benefits of high compression with maximum breathability. This state-of-the-art fabric is crafted from resilient nylon that wicks away sweat and enables full range of motion—whether you’re at bootcamp or barre class. 75% Nylon/25% Elastane