IQOS 3 DUO:
Consists of two units: a holder, which is used to consume HEETS tobacco sticks; and a pocket charger, which is used to recharge the holder. When the holder is fully charged, you can consume two HEETS tobacco sticks in a row. The pocket charger supplies the holder with enough power for a total of 20 HEETS tobacco sticks.
IQOS 3 Multi:
Is the compact all-in-one solution: Its holder and pocket charger are one unit. When fully charged, you can consume 10 HEETS tobacco sticks. That’s why many people choose to use IQOS 3 Multi as a second device, such as in their car.
IQOS 2.4 Plus:
Is the entry-level model. When the holder is fully charged, you can consume one HEETS tobacco stick, while the pocket charger supplies the holder with enough power for 20 HEETS tobacco sticks.
The models IQOS 3 and IQOS 2.4 are predecessor models and no longer available, but are very similar to IQOS 3 DUO.