ND Fader Filter for DSLR Filmmaking?

Just curious if anyone could recommend any good ones for under $100? I shot a music video a week ago and it had over exposure. I was not expecting this since im new to filmmaking. Also has anyone tried these? Are they any good? Worth the money? http://www.amazon.com/Polaroid-Multi-Coated-Variable-Neutral-Density/dp/B004GYXRM4/ref=sr_1_1?s=electronics&ie=UTF8&qid=1325122066&sr=1-1