From Free People:
Shift into sport mode in this muscle tee, featuring a super-soft, sweat-wicking fabrication with a flattering boat neck and tube silhouette.
Fit: Relaxed fit; fitted at bottom; tube silhouette; muscle sleeves
Features: Sweat-wicking fabrication; four-way stretch; breathable; ruched side detail; boat-neck; muscle tee sleeves with oversized opening