Steel roller buckle. Ventilated back panel for comfort. Anatomically-correct design. 30% polyester/30% EVA/20% nylon. The Nike Strength Training Belt offers a supportive design for heavy-duty training in an adjustable fit for comfort. #Steel roller buckle. #Ventilated back panel for comfort. #Anatomically-correct design. #30% polyester/30% EVA/20% nylon.