I bought these replacement heads because they were advertised as compatible with all oral b electric toothbrushes and they do fit my oral b electric toothbrush bought recently to replace old one, but, the brushes are softer and the heads a little smaller compared to the usual Oral B toothbrushes.
The advantages to the smaller softer brushes are that they are better if you suffer from sensitive teeth and gums, but if you want a slightly more firmer brush and bigger then these might not suit except for the price and the quantity of brushes you are getting which is why I bought them.
However, time will tell, as to how long they will last before I have to replace the brush again because they are softer, this might mean that they will need to be replaced more often compared to the firmer brushes.
They will do for now, as they are cheaper than the regular Oral B refills heads.
Also the seller I bought them from shipped these from the USA but arrived very quickly.