The NanoPro Magnetic Nd 0.9 filter provides a 3-stop reduction in light while darkening the entire image. The Nd 0.9 filter attaches magnetically to the magnetic adapter ring (sold separately) and can be quickly attached and removed safely and securely.Haida's NanoPro Magnetic filters can be stacked with other magnetic filters from Haida without vignetting.Note: This filter does not include a magnetic adapter ring, which must be purchased separately..