THIS ITEM IS A SET OF FOUR COMMAND B2C4-0016 ER16 COLLET CHUCKS DESIGNED FOR BT30 SPINDLE TYPE. THE CHUCKS FEATURE COOLANT-THROUGH CAPABILITY. KEY DIMENSIONS INCLUDE A PROJECTION OF 2.64 INCHES, AN OVERALL LENGTH (OAL) OF 4.60 INCHES WITHOUT THE BUTTON, A NUT OUTER DIAMETER OF 1.25 INCHES, AND A BODY DIAMETER OF 1.80 INCHES. THE MANUFACTURER IS COMMAND, AND THE MPN IS B2C4-0016.