Luxilon M2 Pro 125 Tennis String is an all new string that uses a multi/mono technology that provides the durability of a monofilament with the playability of a multifilament. This technology creates M2's variable flex for more control on hard hits and more comfort on soft hits. All of the benefits of a hybrid - now in one string. Use Luxilon M2 Pro for added playability vs. Luxilon M2 Plus for added durability. Luxilon Tennis String wrz9985