The 2.5 Factory Series Shocks are designed for off-road performance, rather than being a balanced performance shock like the standard Fox 2.0s. The 2.5s (as their name implies) are 2.5" in diameter, have more aggressive valving, and have a built-in piggyback reservoir that all kick up their price over the 2.0s. As far as ride goes, the 2.5s will likely be fairly stiff on road while being much more capable off-road than the standard 2.0s. The Fox 2.0s have a nice on-road ride and offer a huge improvement in ride quality while having very good off-road performance, though not as good as the Fox 2.5s.