bump to get this thread read by everyone! recently picked up two clearance tiffen 67mm uv filters for $5 a pop, got a pckg of the respirator filters for around $15 (not as easy to find as youd think! most stores only carry the masks or the sets with the respirator included, which is much more expensive)... results are impressive!!! i use a neutral white balance card for most situations, but for certain situations and when you know the light is constant on the source, this disc kicks some ACE... better at mixed lighting than a traditional WB card also, as it creates a diffused light pattern for the custom WB... and best of all it took about 5 minutes to cut out the filter and screw the two filters together (didnt bother with the pretty plastic glued onto the front, thats cosmetic anyway, and it doesnt look bad at all without it) and saved me about 90 bucks! and for an extra $10 each, i can make about 9 more!