20Mm I.D. Hsk-63A Guhrojet Peripheral Coolant-Fed Shrink Fit Holder, 120Mm Gage Length Hsk-A To Iso 12164-1 / Din 69893-1 | Balanced To G2.5 / 25,000 Rpm | For Tool Shank Tolerance H6 | To Din 69882-8 | Includes 4 Or 6 M6 Balancing Screws | Optimized For Cutting Tools Without Internal Coolant Ducts | With Coolant Ducts In The Bore For Directing Peripheral Coolant Directly To The Cutting Tool, Improving The Machining Process And Extending Tool Life | Includes Setting Screw, Series No. 4977 With Axial Force Dampening For Perfect Runout Accuracy. A Gripping Principle: When Shrink Fitting Tools Into Shrink Fit Chucks, The Decisive Factors For Ensuring The Safe Clamping Of The Tool In The Tool Holder Are Solely The Heating And Cooling Of The Tool Holder. The Heating Process Expands The Shrink Fit Chuck Enabling A Tool To Be Inserted Or Withdrawn Respectively. During The Cooling Process It Contracts Again And Clamps The Inserted Tool With Maximum Clamping Force. Series No. 4755, Order Code 220.0630. Made In Germany, Guhring Part #9047552200630