For maximum tissue penetration and precise massage, 4D rollers give users a deeper tissue massage. These 4D rollers can rotate and reach different angles that 3D rollers cannot. In addition, in a 4D massage, the rollers can automatically accelerate or slow down to focus on tense muscles. The purpose of the 4D technology development was to make the massage chair more capable of reproducing the massage a therapist can offer. The massage intensity is relatively higher in a 4D massage chair (4 directions) than a 3D one (3 directions).