Give your hair a chance, in as little as 16 weeks, without medication

Any of them. The difference is the number of diodes, and therefore how much of the scalp is covered. Which one suits you depends on your budget and your needs.

Yes. If you are also using medication, discuss combined use with your doctor.

Trials commonly used protocols of three 30-minute sessions per week. Follow the instructions supplied with the device. Total daily use should not exceed three hours.

Use is painless. Mild warmth is normal. The cap is light and comfortable to wear.

In scientific studies, changes in hair growth were typically reported after twelve to sixteen weeks of regular use.

More diodes mean more of the scalp is covered. The devices used in trials generally covered a large area evenly.

Most published research is based on studies using low-level lasers. Laser light is more coherent and more directional than LED light.

The optical output power of one laser diode is 5 mW. That is the power of the emitted light, not the electrical consumption. The total optical peak power by model: 128 diodes 0.64 W, 208 diodes 1.04 W, 312 diodes 1.56 W. The device works in pulsed mode, so the average power is 41.6 per cent of that: 0.27 W, 0.43 W and 0.65 W.

With outer dimensions of roughly 165 × 190 mm, the irradiated area of the 312-diode cap is about 246 cm². The device works in pulsed mode with a duty cycle of 41.6 per cent, so the average power is 0.65 W. That corresponds to about 2.6 mW/cm² average power density, and the energy dose of a 30-minute session is about 4.75 J/cm². For the other models: 208 diodes 3.17 J/cm², 128 diodes 1.95 J/cm². This is a figure calculated from the manufacturer's data, not a measurement. The actual dose is lower, because some light escapes at the edge of the cap and some is absorbed by the hair. For comparison, published studies of similar devices reported doses of roughly 2.9 to 4.2 J/cm² per session.

650 ± 10 nm, meaning the diodes emit between 640 and 660 nm. This is recorded in the laser safety test report. Most LLLT studies on hair were carried out in the same red range, between 630 and 680 nm.

Pulsed. According to the manufacturer's data the device runs at 6.94 Hz with pulses of 60 milliseconds, which is a duty cycle of 41.6 per cent. The diodes are therefore lit for about 42 per cent of the session. This is common for devices with many diodes and limits peak current and heating.

The cap comes in two sizes: standard with an inner circumference of 58 cm, and large at 62 cm. That matches the industry standard. The cap does not need to be tight; a little room at the sides is fine. It is a device for use at home, not a fashion cap. Put it on while sitting upright.