NO SPRING INCLUDED. MUST PURCHASE SEPARATELY IN DROP-DOWN MENU ABOVE. We&';ve testing several coil shocks with reasonable price tags on our Stumpjumper EVO test rig, and we found the RockShox Vivid Coil Ultimate to be the best option! This shock is super consistent and adjustable, and the HBO (hydraulic bottom out) feature is worth it&';s weight in gold for this bike&';s suspension design. When testing other coil shocks without HBO, the bottom-outs were hard and frequent... even with a progressive coil spring. This kit includes: (1) RockShox Vivid Coil Ultimate in 210x55 (1) RockShox Mounting Hardware in m8x20 (for the front eyelet) (1) Specialized Shock Hardware Kit for Stumpy EVO (for the rear eyelet) HOW TO FIND A COIL SPRING RATE To finish the kit, simply choose a spring in the color and rate of your choice from the drop-down menu. To find a spring rate with pretty close accuracy, use our Spring Rate Calculator and enter your weight when geared up, stroke (55) and rear wheel travel (150). When the calculator gives you a spring rate number, simply "spring down" and purchase a spring rate that is 50# less than what number it tells you.* That should set you up around 27-32% sag. However, you will want to measure sag yourself and ride it to see how it feels. If you prefer different riding characteristics you will need to purchase another spring separately. For example, I (Mike) am 150 pounds the spring calculator says to use a 461# spring rate. However, I "spring down" by 50 pounds which is 411#, and the closest spring rate to that is 400#. With the 400# spring rate, I am at 28% sag which feels perfect on this bike. Also, there is no performance difference between the Red and Black springs. Just pick your favorite color! The Lost Co&';s spring rate recommendations based on weight: table { width: auto; border-collapse: collapse; } th, td { border: 1px solid black; padding: 8px; text-align: center; vertical-align: middle; } td { text-align: middle; } Total rider weight with gear Recommended spring rate 90-110 250 110-125 300 125-140 350 140-155 400 155-170 450 170-190 500 190-205 550 205-220 600 220-240 650 240-255 700 *All bikes react to spring calculators differently, and that&';s just how this bike reacts and works in the real, physical world.