On the shocks, Yes, F & S mean Fast and Slow. These are valves to control the rate the fluid travels through the valve. If there are two valves, the one on the bottom is for rebound. This controls how fast the shock extends back out after taking an impact that compresses it. You want some restriction here to reduce the bounce effect. The other if it has it will be on top and its is for compression, that is how fast the shock compresses say..when you hit a rock. This can make it feel stiff to mushy. In either consider them as hydraulic valves that control fluid flow. It either goes through faster or slower. Tuning these is very important for ride and control as together they effect every aspect of your experience.