4' x 100' 7mil on Black MylarThe highly reliable black mylar has been designed for delivering optimum light to the plants with its 98% reflective power. The thick sheet measures 7mil, which ensures strength and makes it tear resistant. With the installation of the black mylar, there won't be any heat spots, so exposing plants to light in the presence of black mylar won't leave you stressed. Tear Resistant: The 7mil thick black mylar is tear resistant, so you can stay rest assured