The head lasts up to 3 months of use, after which they begin to fall apart, lose their effectiveness, and in addition, bacteria accumulate on them. Fortunately, the heads are equipped with blue bristles that fade after 3 months, so you know its time to replace the heads. Compatibility TrueLife SonicBrush K series. See also other products of the brand TrueLife, which are in the Electronics under the tree, Toothbrushes and Mouth and teeth categories. You can buy the product with a 0% discount. If you are not sure about the choice of this product, be inspired by the category of Sonic replacement heads.