If you know an avid tennis player that breaks their strings a lot!  Why not help them invest in a tennis stringer.  Get tips from the USRSA on how to string rackets.  You can also find such videos on Youtube.

FIND OUT HOW TO STRING RACKETS FROM THIS GUY: YULITLE

STRINGERS ON SALE(FREE SHIPPING!): Click on picture for buying options)

Gamma Progression II 602

Gamma Progression 602 FC

Gamma 6500 ELS

Gamma 6004