I use HighTech and they work pretty good for me..
As everybody else has said.. no filters are in anyway scratch resistant but after using them on
two trips with heavy uses there's no scratches that messes up the pictures..
You do need something to remove the dust with before and after each use, I use the lens cleaning kit
with a "rocket blower" and cloth..
I bought a 1-2-3 kit and a 10 Stop with Lee holder and 77 and 82 Wide angle adapters..
Only used the 1 stop to stack, never alone so I haven't had much use of it..
Then again, I use the 10 stop most so +/- 1 stop doesn't make much of a difference..