The extension of the hands after contact is an essential part of the swing and keeps the bat on the proper plane which allows for more power and consistent contact.  Extension is basically taking the arms from a bent position to a straight position with the top of the bat facing toward to pitcher.  Players with poor extension tend to make weak contact and fail to drive the ball well to all fields.  Players with good extension tend to have the following things in common:    

 

1.  The top hand remains palm up as long as possible.

2.  The head remains over the back leg through extension with the back shoulder coming under the chin.

3.  The space or gap between the arms is maintained until the top of the bat faces the pitcher.

4.  The body conitnues to have tilt toward home plate

5.  The head is tilted down toward the contact point.