New from Haida, the rear lens filter kit is designed specifically for the Sigma 14-24mm F2.8 DG HSM Art Lens for Canon EF/Sigma 12-24mm F4.0 DG HSM Art Lens for Canon EF to allow you to use solid ND filters without vignetting on the ultra-wide angle lens. Each solid ND filter is made of tempered glass with an anti-color cast multicoating.