A massage chair differs from an ordinary armchair in that it has a rail with moving massage mechanisms and an air-cushion system. Models are grouped by mechanism type into 2D, 3D and 4D.
A 2D mechanism moves up and sideways, 3D adds depth pressure, and 4D also varies the rhythm, so the massage feels closer to human hands. The longer the rail, the more of the body is covered: an SL rail works from the neck down to the thighs.
Measure the space before choosing: a chair needs room to recline unless the model has a zero-wall function.
