The factory Buna rubber used in OEM o-rings breaks down from heat and oil exposure, causing oil leaks and loss of pressure to the VANOS unit. Before now the only way to replace the o-rings was with a new solenoid, or to guess at the correct size (and material) for replacements form your local parts store. Now ECS Tuning has the perfect solution: this kit includes enough o-rings to replace all the o-rings on all four of the S85's solenoids. No more spending thousands of dollars and no more guessing!