Quick answer: a 3D massage chair moves its rollers up and down, side to side and in and out, so you can choose how deep the massage goes. A 4D chair does all of that and also changes the speed and rhythm of the rollers as they move. In the ROTAI UK range, the A39 and RT6891 are 3D, the S56Pro is 4D, and the A68Pro has both a 4D and a 3D mechanism.
2D, 3D and 4D in plain English
- 2D: the rollers move up and down your back and side to side. The depth is fixed.
- 3D: adds in-and-out movement, so the rollers can press further into the muscle or stay light. You can usually set the depth and width.
- 4D: adds control of speed and rhythm, so the rollers can slow down, speed up and pause within a single movement instead of running at one steady pace.
3D in the ROTAI range
The ROTAI A39 (£1,560) has a 3D roller that adjusts in width from 3.5 cm to 20 cm, so it can work narrowly along the neck or wide across the shoulder blades. The ROTAI RT6891 (£1,660) has a 3D mechanism with 6 speed settings, 3 width adjustments and 3 focus settings, running on an SL-track that reaches the hips and thighs.
4D in the ROTAI range
The ROTAI S56Pro (£1,960) uses a 4D SmartSync mechanism with four separate motors for walking, tapping, kneading and radial movement. The ROTAI A68Pro (£2,560) has a 4D and a 3D mechanism on one ultra-long SL-track: the upper mechanism travels up to 840 mm and the lower one up to 830 mm, overlapping by 360 mm across the middle of the back.
Side by side
| Model | Mechanism | Track | Price |
|---|---|---|---|
| A39 | 3D, 3.5–20 cm width | Not stated | £1,560 |
| RT6891 | 3D, 6 speeds, 3 widths, 3 focus settings | SL-track | £1,660 |
| S56Pro | 4D SmartSync, four motors | 125 cm SL-style track | £1,960 |
| A68Pro | 4D and 3D, two mechanisms | Ultra-long SL-track | £2,560 |
Prices as of November 2026. Each product page shows the current price.
Which should you choose?
- Choose 3D if you mainly want a strong, adjustable massage for the neck, shoulders or lower back, and want to keep the cost down. The A39 suits the neck and shoulders, the RT6891 the lower back and hips.
- Choose 4D if you will use the chair most days and want the massage to vary in pace rather than repeat the same rhythm. The S56Pro is the lowest-priced 4D chair in our range.
- Choose a dual mechanism if you want the upper and lower back worked at the same time. That is the A68Pro.
Moving from 3D to 4D in our range costs £300 to £400: the RT6891 is £1,660 and the S56Pro is £1,960. For the full picture, see which ROTAI massage chair should you buy and our massage chair buying guide.
Questions about 3D and 4D
Is 4D better than 3D?
Not automatically. 4D adds control over speed and rhythm, which many people like for daily use. A well-made 3D chair still gives an adjustable, deep massage and costs less.
What does the D stand for?
Dimension. Each extra dimension describes another way the rollers can move: 2D is up, down and side to side, 3D adds depth, and 4D adds changes in speed and rhythm.
Which ROTAI chairs are 4D?
The S56Pro, with its 4D SmartSync mechanism, and the A68Pro, which has a 4D and a 3D mechanism.
How much more does a 4D massage chair cost?
In the ROTAI UK range, the lowest-priced 4D chair is the S56Pro at £1,960, which is £300 more than the 3D RT6891 at £1,660.