Original LEE Filters 105mm Landscape Polariser screw-in is designed for the 100mm Foundation Kit holder, 105mm Front holder Accessory ring is required to attach it - found here.
The Polariser specifically designed for the LEE100 system can be found here.
The 105mm Landscape Polariser is a slimmer than the 105mm Circular Polariser and will go down to 16mm without vignetting when used with a two slotted filter holder on a full frame 35mm sensor. This Polariser also comes with an added advantage. It has a slightly warm bias, so not only is the photographer able to remove glare from shiny surfaces, or increase the contrast between blue sky and white cloud, they can also enhance the greens, browns and golds that are so often associated with photography in the landscape.