The Canon RF 10-20mm F4 L IS Rear Filter Kit is a dedicated accessory designed specifically for use with the Canon RF 10-20mm F4 L IS STM lens. As an ultra-wide zoom lens, the RF 10-20mm features a deeply curved front element that makes traditional front-mounted filters impractical -- this rear filter solution allows photographers to use gel or sheet filters at the rear of the lens, providing a convenient and optically sound method to apply neutral density, colour, or other creative filtration without compromising the integrity of the front element. Engineered to Canon's L-series standards, this rear filter kit is the recommended accessory for videographers and photographers who need reliable filtration control when shooting with this exceptional wide-angle lens.