Reducing full-load tri-axial vibration while increasing impact energy, the DH40MRY SDS Max rotary hammer uses three mechanisms to reduce vibration felt by the user-the original design counterbalance, a transitory unit in the top of main handle, and a new rotating vibration insulating mechanism in the bottom of the main handle. The counterbalance design responds to the force created by impact. Hitachi Power Tools. 800-829-4752.