Officially you can check the different section numbers from TET Atlas.
https://atlas.transeurotrail.org/
Remember these previews are not necessarily correct.
The Sections will have updates after this!

Section 01

Our “Main Section” That goes from Helsinki to Norway. This Section has the most variation in landscape and in different road types.

Section 02

This section starts from Renko and connects back to section 1 in Kuusamo. Section 2 has some interesting historical landmarks and nice technical part in the north before Kuusamo.

Section 03

Section 3 is from Turku to Enontekiö goes in the most western parts Of the country. There are some nice technical parts between Raahe and Oulu.

Section 04

Section from Vaalimaa to Raate road. This section goes very close to Russian border and you will probably meet the border patrol. You need to be careful that you have enough gasoline after Lieksa.

Section 05

Section in southwest Finland. Has some nice technical parts.

Section 06

Section from the eastside of Helsinki to north.

Section 07

Section starts from the westside of Taivalkoski and it ends to the most northern point of EU.

Section 08

Section in the “Middle of Finland”. Some nice technical parts and soft sand.

Section 09

Section between sections 01 & 02 (from the lake Ala-Luosta to the Lake Oulu)

Section 10

From East to west with Thousands of lakes…

Section 11

Section to Niekka Hill

Section 12

Section between sections 03 & 02 (Pudasjärvi, Taivalkoski). It has one manual ferry!

Section 13

Section “Lättis”. The most famous motocafe.

Section 14

Section from Helsinki to Vaalimaa.

Section 15

Section between 3 and 2 (from Siikainen to Hämeenkyrö)

Section 16

Section between sections 02 & 03 (from Kinnula to Eskola)

Section 17

Section between sections 03 & 01 (Tervola, Kemijärvi)

The sections has updates all the time so remember to Download the latest GPX before you go to the TET. The right place to download the GPX file is transeurotrail.org/finland