Gosen-OG-Sheep Micro 660 Tennis String Reel-() The OG-Sheep Micro tennis string offers a superior balance of playability and durability. This has the same great quality of synthetic gut strings that players know and love... Gosen Synthetic Gut Stings | All Around Performance | Great Value String Size - (17G) | Color - (Natural) Authorized Gosen Dealer. All racquets are strung and ready for the courts! SEE SELLER DETAILS FOR RETURN POLICY.