These rotary unions are designed for the passage of coolant, air, MQL, and dry running. The special design allows mounting inside the spindle to minimize space requirements. The use of a special seal design enables the spindle to operate dry without opening the seals, eliminating any fluid loss caused by the continuous opening and closing of the seals. The compact design allows these unions to operate at high rotation speeds (up to 40,000 RPM) and high pressures (200 BAR).