Comments about Smith-Victor Smith Victor BD80 2 Leaf Barndoor/Filter Holder Combo for 8" Reflectors.:
Light-weight construction is probably not suitable for the working pro, or on location, but they are fine for my in-home part-time studio. They will work with any 7-7.5" diameter reflector.
I use them on 3 of my 4 StudioMax III light setup. They are great for controlling hair lights or side lights. I also find it useful for shaping and controlling the main as well.
The built-in color filter holder is very convenient.
A four leaf barndoor would be better, but you can't beat the price.