A number of different toolholder adapters can be mounted into the precision ground cylindrical recess of the PTB balancing spindle:
SK 30 to SK 50 (PTB 21.2) SK 30 to SK 40 (PTB 7.2) HSK 25 to HSK 100 (PTB 21.2)     all forms HSK 32 to HSK 80 (PTB 7.2)     forms A to D	Toolholder adapters SK and HSK
The test rotor with SK 40 or HSK 63 maybe used to verify the balancing functions, calibration as well as the accuracy of measuring of the PTB.	Test rotor HSK 63