Bitvae BV SDS2 Toothbrush Replacement Heads (Black) The soft DuPont fibers used in the Bitvae SDS2 toothbrush replacement heads are shaped in a "W" pattern to better reach the gaps between teeth. Dentists recommend replacing them every three months to maintain brushing effectiveness, which is why the replacement heads are equipped with fibers that fade over time - when they lose their color, it's time to replace the head with a new one. Note: the color of the bristles may vary. BrandBitvaeColorBlackCompatibilityBitv ae SDS2