Non-vented. All battery boxes meet ABYC standard E-10 and U.S.C.G. Specification Number 183.420 as an OEM-installed battery hold-down system. Polypropylene construction for total acid resistance. Hold-down straps resist 350 pounds of force, nearly four times the U.S.C.G. requirement. Battery boxes are drop tested in temperatures ranging from -20F to +120F. Mounting hardware is included.