Are you kidding? If they aren’t branded, they certainly aren’t manufactured by OralB. OralB no longer has a patent on the brush heads, so like K-cups they can be manufactured by anyone who wants. Like these. The authentic ones are about 4x the price.

Amazon even sells their own brand.

And even many branded products sold on Amazon these days are not legal knockoffs and mislabeled as authentic. I wouldn’t trust anything sold by third party sellers if I was worried about getting the true brand’s product. Then again. Most consumer stuff is just plastic crap and it doesn’t matter who’s making it.