Nukeproof rockshox vivid steel spring 25 2 75ultimate quality steel shock spring getting the correct spring weight on your coil shock is crucial and can make the difference in getting the best out of your suspension the nukeproof vivid spring has a 38mm inside diameter to fit rockshox vivid coil shock units how do i choose the correct sizethere are three important things you need to know about your set upthe stroke of your shock this is the actual travel of the shock itself to measure