Maximum hair length is a measurement determined by your genetic code. Products can not improve your natural hair limit.  Hair appears to stop growing at a certain length because each hair strand has a growth phase (anagen phase) followed by resting (telogen) and shedding (catagen) phases. Once the growth phase ends, the hair will no longer get longer, and it eventually falls out, replaced by a new hair. The length achieved during the anagen phase varies per individual and is influenced by genetics, health, and other factors.