All new and bang up to date with the most comprehensive feature list of any mountain bike on the market, there's a Gen 7 Fuel for pretty much every one. 

Features in common across all models:

• Adjustable suspension leverage rates.
• Modern geometry with taller stack height compared to Gen 6 Fuel.
• Size specific chain stay.
• Internal frame storage.
• Straight seat tubes for maximum dropper post insertion.
• ZS headset cup can be replaced with angle adjust headsets (Treks' own available here).
• Chainstay and downtube protection.

Three varieties of Fuel are available, all using basically the same frame but with different rocker linkages and suspension. If you decide you want to change your bike to one of the other version later down the line, it's a case of changing the suspension and linkage.

• EX: 29" wheels,150/145mm travel (Size S has mixed wheel sizes)
• LX: 29" Wheels, 170/160mm travel
• MX: Mixed Wheels, 16/150mm travel