The Leica filters for the Leica M-System are made of optically pure glass, parallel plane ground and precisely annealed, so the full performance of the Leica M lenses is retained even with a filter attached.
Haze filters provide benefits of correction for Ultraviolet(UV) light which can register on images as a bluish cast and can obscure distant details. Ultraviolet filters allow you to correct for the UV effect to varying degrees.
The UV-Haze filter is helpful when photographing scenes where increased haze threatens to make your photographs indistinct in color and clarity.