I recently bought a hieie electric toothbrush, only to find that purchasing replacement brush heads proved very difficult to find (actually, impossible for me, but I might not be all that good at finding them).Rather than treating the toothbrush as a throw-away, I thought I would take a chance on these. From the pictures in the description, they appeared as if they might fit. Unfortunately, they didn't fit my toothbrush, so I took a look at making a minor modification. It turns out that a number 23 drill bit is the right size to enlarge them so that they fit perfectly on my toothbrush. I now have 16 replacement brushes (I destroyed 4 of them in my experimentation) at a cost of about $1 each. Quite a bargain, in my opinion.As an added benefit, these replacement brushes have a softer shell than the originals that came with my toothbrush. You might wonder why that would matter, and the answer is: On this style of toothbrush the entire brush head vibrates rather than the bristles. Because the outer shell of the originals is a harder plastic, they cause an annoying vibration when you touch your teeth with anything but the bristles. Having a softer coating on the outside of the brush absorbs some of that vibration, making brushing my teeth a more pleasurable experience.