Decent quality. Cost effective sonic toothbrush replacement heads.
This seems like a credible replacement for sonic toothbrushes. However, the cavity that accepts the metal extension is smaller than expected. To be fair, though, it was not tested with a Philips brand sonic toothbrush; the host brush is a different brand sonic toothbrush.  So, it is possible that it's fully compatible with the Philips brand.  (Although, I've attached other 'compatible' sonic toothbrush heads with success.)<br />Attached are photos to show real world images of the toothbrush heads. I included pictures of the product attached to a sonic toothbrush. You can see that it cannot fully attach, leaving a gap.  Also want to note that it took considerable effort to 'force' the brush head onto the metal spindle. When powered, the brush did appear to function as expected.<br />Overall, the brushes appear to be identical to my original sonice toothbrush head. I couldn't measure the diameter of the receptacle. However, from attempts to attach it, the hole was obviously too small.<br />Since, I cannot be fully certain of the compatibility with the specified Philips sonic toothbrushes, owning a different brand, I will rate this product based upon the apparent quality of materials and manufacture. As such, it's a very credible product, and will receive a 4.5 star rating.
Rating: 5 stars