Metal material, Sturdy metal construction, good bearing capacity and durable in use. Recessed slots design, so battery won't make contact with tray fasteners. The clamping range is adjustable. Clamping width range is 5.9 inch - 8.66 inch (15-22cm) and clamping height range is 5.5 inch-9 inch (14-23cm). Only fit for batteries within 13inch x 7.5inch (33x19cm). Battery tray and hold down clamp kit. Fit for automotive or marine use.