its the expensive bougie ones. oral-b has mutliple lines. oral-b 100-1500 line is your standard non-smart ones more durable. its only if you buy something higher than that which is 100-200$each like the IO series. if you for some reason want to only use IO replacement heads that is expensive too, always get off-market replacement heads.

sonic toothbrush apparently is a different company(sonicare).