I bought these to put on a standard Braun Oral-B electric handle which had previously been using their original simple round brush-heads, and they fit perfectly.
The design is very similar to that of the original standard round head apart from the addition of their "floss action" components which are simply flat wedges of plastic that are clearly designed to get right in between your teeth. I absolutely hate flossing (I can't actually physically fit floss or even tape between most of my teeth), so I figured these brush-heads would be the next best thing.
On first use I got the distinctive taste in my mouth I get upon attempting to floss with tape, and a minor amount of gum-bleeding, indicating that these brush-heads really do work like they say they do. Subsequent brushings have not produced the same effect, which I can only put down to the fact that the "floss action" is now so regular that my gums are used to it and the bacteria aren't building up between my teeth. I therefore conclude that these do exactly what they say on the tin.