Review (2/5): Perfectly comfortable for brushing, but a loose fit on the brush
These brush heads are perfectly average in terms of design and comfort. They presented no difficulties with brushing whatsoever and were comfortable to use.
My big problem was they they did not seat firmly onto the brush's metal attachment, and thus fell off several times during my brushing session. The information on this page clearly indicates that they are compatible with ALL (emphasis theirs) Oral-B electrich toothbrushes, with the exception of Sonic models (which I do not have, I have the Oral-B Deep Sweep 5000).
As such, I cannot really recommend them. They will brush your teeth, but only if you're comfortable catching it in your hand every 30 seconds or so.