The FIM World Enduro Championship (WEC) is the world championship series for enduro, a popular form of off-road motorcycle sport. The championship currently features three classes (E1, E2 and E3), along with separate categories for junior and female riders. The WEC was first organized in 1990. All rounds include an enduro test, a motocross test and an extreme test.

Enduro 1 (E1) – 100 to 125cc 2-stroke or 175 - 250cc 4-stroke
Enduro 2 (E2) – 175 to 250cc 2-stroke or 290 - 450cc 4-stroke
Enduro 3 (E3) – 290 to 500cc 2-stroke or 475 - 650cc 4-stroke
 
http://www.enduro-abc.com/