The RockShox Oil Height Tool for Reverb dropper post is used during overhauls/rebuilds to remove all the excess fluid from inside the post head. It must be used in conjunction with the syringe from the RockShox Reverb Hydraulic Bleed Kit sold separately).

In case you are wondering, RockShox factory recommended service intervals are every 100 hours of riding for the remote and hose bleed. Keys, topcap seals, and seal head seal replacement should also be done every 100 hours of riding. A complete seatpost overhaul is recommended after 200 hours of riding. It should be noted that servicing Rockshox components does require specialized bicycle knowledge and tools.