- Constructed from proprietary Fox super light steel (SLS) - 1.38" inside diameter fits Fox VAN/DHX/DHX2 -All SLS springs are orange and are marked with their spring rate in lbs/in (in 25 lb increments) and the maximum travel of the shock that they are designed to be paired with. -All standard steel springs are black and are marked with their spring rate in lbs/in (in 50 lb increments) and the total travel of the spring itself. Standard black springs should only be paired with shocks having less travel than the travel marked on the spring itself.