Quote Originally Posted by M_Six View Post
I have the BB as well. My nitpick is that the Canon version fits the 580EX II only. I have the 430EX II and I added some velcro strips above and below the flash head to flesh it out a bit, but the BB still doesn't fit snugly, which causes droop. Unless they've come out with another version, I don't think the BB will fit the 660 EX-RT either.
The FX-5 is the correct one for the 430EX/430EX II. You apparently have the FX-3, which is for the 580EX/580EX II. I have an FX-3, and it fits just fine on my 600EX-RT.