The terms
SL track, 4D rollers and body scan explained
- SL track: the rail the massage rollers travel on. An S track follows the curve of the spine; an L track continues under the seat to the glutes and hamstrings. SL combines both, so one pass covers neck to thighs. All three chairs here are SL track.
- 3D vs 4D rollers: 3D rollers move up, down, side to side and in and out of the back. 4D adds variable speed and rhythm within the stroke, which feels closer to a therapist's hands. The C13 and C80 are 4D; the C79 is the entry model.
- AI body scan: the chair measures your height and shoulder position before a session and maps the rollers to your body. On the C13 4D Smart and C80.
- Zero gravity, heat, airbags: reclines that take weight off the spine, lumbar heat and air compression for arms, calves and feet. Confirm per model on the listing.