Yamaha RZ350 (US Versions) Fork Caps with Preload Adjusters CNC Billet Fork Caps with Pre-load Adjusters. Note: These are for the 84/85 US RZ350 (35mm fork tubes) The common misconception with pre load adjusters is that they increase spring tension. What they really do is allow you to adjust sag correctly. With all the suspension mods happening with these bikes it's easy to end up with the wrong sag. Even with the correct spring rate for your weight, you cannot always get the optimal sag without opening up the forks and adding spacers or cutting springs. These give you about 20mm of adjustment, which when combined with the proper spring rate, will allow you to set sag perfectly and adjust it for your weight and riding style. These also have graduation lines on the stems for easy reference when adjusting. Note: Fork tube size is 35mm,  cap thread size is 31mm x 1.5 pitch. Sold in pairs. Kit includes 2 fork caps with pre-load adjusters, o-rings, fork spring discs and installation instructions. Yes you will lose the air forks with these adjusters, but air in forks doesn't work very well as it compresses exponentially. Switching to some of the better after market fork springs and these adjustable pre-load fork caps will really dial in your suspension.