Bitvae D2 Toothbrush Replacement Heads (Black). The dark blue bristles on the toothbrush head lose their color intensity with use - when they have completely faded, it's time to replace them with new ones. The specially designed bristle layout adapts better to the shape of your teeth, reaching the gaps between them. These heads are intended for the Bitvae D2 toothbrush. The package contains four pieces.