The Chinese have gotten much better with the Oral B toothbrush head counterfeits.
I bought some on eBay, advertised as genuine but not. The packaging was near perfect. The only thing that gave them away was the different mouth-feel and two misplaced mold release marks.
Genuine Braun dual-action brushheads have two divits on top of the brushhead. The copies have the two divits on the side.
I sent a note to the seller warning him that some counterfeits might have gotten into his supply. Seller refunded me.
If you get counterfeits from Amazon I am sure the 3rd party seller will refund you.
I’ve bought both the brand name and cheaper knockoff Oral-B electric toothbrush heads. Haven’t been able to distinguish them yet in terms of quality and performance. YMMV.