By cons, days after 2 weeks of use, and despite a very thorough rinse, the interior of the head is filled with black mold. It's disgusting and not at all hygienic.
I thought we badly rincions heads, so we repeated the test with 4 heads, replacement of the brush and washed with water after each use, rinse well inside, and putting them to dry vertically on sink: but the problem is for each new head.
I honestly do not know if the problem is with these heads which are generic, or if there is the same with the heads of the brand Oral B. In fact, I changed brush mark without trying the Oral B (tired of wasting money and throw plastic ds nature).