The WonderPana Free Arc XL provides the freedom to use and rotate the rectangular 80 filters and round 186mm filters on your Wide and Ultra-Wide Angle Lenses. The all-metal Core attaches directly onto the lens with a secure mounting system. With The Core in place, you can now mount any of Fotodiox's 186mm round filters. For even more filter flexibility, mount the WP80 Filter Brackets (these mount without tools on either side of The Core). Once attached, you can easily slide in the WonderPana 80 square filters, which are among the largest and most durable in the business. With the Free Arc, the filter stage is rotatable 360 degrees. The Wonderpana Free Arc XL can accommodate either two square filters, or one round and one square simultaneously. Fotodiox Pro ND Filters are true neutral density filters designed to darken the image. They feature an even, neutral gray color for creative photography applications. The ND32 filter offers a +5 stop EV value which allows you to slow down the shutter speed or use a larger aperture in bright light conditions. The Graduated Neutral Density darkens the sky while leaving the foreground unaffected, perfect for shooting sunset or sunrises where the sky is blown out and the ground is dark, allowing you to capture an image closer to what the human eye naturally sees. These two filters combined are a perfect combination for times when you want to darken the overall scene and darken the sky even more so, such as beach or snow sunsets & sunrises for example. Fotodiox ND & Grad ND filters are a true neutral grey and do not color cast the images. PLEASE NOTE: The WonderPana Free arc XL you see on this page is custom engineered to fit the Canon EF 11-24mm f/4L USM Lens. It will not fit other lenses, so it's important that you chose the correct Wonderpana Core system for your particular lens model. You will have to remove your lens from the camera in order to mount the filter holder.