There are a number of wide angle lenses where it is not possible to fit standard filters or holders because the way the barrel of the lens is configured. Prominent amongst these is the Nikon 14-24 but there are many others including the Canon 4L and the Sigma 8-16 and 12-24. The new Hitech Lucroit holder was designed by a Spanish Engineer (who was also a photographer) who wanted to find a solution to both the Nikon 14-24 problem and that of other similar wide angle lenses. The holder fits on the lens by a bayonet mount with a retaining rubber ring which holds it in place. It is designed to take a completely new range of 165mm standard filters with grads in 165x200mm.