I have a 67mm thread Canon lens and bought this filter for it.  The threads on the filter do not allow the filter to thread easily onto the lens.  It takes me minutes of struggling to align the threads with the lens, and even then it screws in with difficulty.  The photos turn out well,  but the threads on the filter make it nearly impossible to use, especially if you must attach the filter in the field with minutes or less of fading light to achieve a shot.

Update April 26, 2016: Two days ago I was out in the field and couldn't get this filter off my lens after screwing it on.  Made the rest of the outing difficult photography-wise.  After I got home and worked on it for awhile I was able to remove it.  I am buying a filter wrench, but the bottom line is easily told -- the threads are not well cut.  My other filters screw on and off the 67mm lens threads just fine.  Only this filter is giving me trouble.
AD2
I have a 67mm thread Canon lens and bought this filter for it. The threads on the filter do not allow the filter to thread easily onto the lens. It takes me minutes of struggling to align the threads with the lens, and even then it screws in with difficulty. The photos turn out well,  but the threads on the filter make it nearly impossible to use, especially if you must attach the filter in the field with minutes or less of fading light to achieve a shot. Update April 26, 2016: Two days ago I was out in the field and couldn't get this filter off my lens after screwing it on. Made the rest of the outing difficult photography-wise. After I got home and worked on it for awhile I was able to remove it. I am buying a filter wrench, but the bottom line is easily told -- the threads are not well cut. My other filters screw on and off the 67mm lens threads just fine. Only this filter is giving me trouble. AD2