High-performance yo-yo string with a "grip guard" sleeve to protect your finger from injury during play. At the time, there was a pending patent assigned to this product. However, I could not find if the patent was officially issued.
The blacked out portion on the back of the card read, 800-525-YOYO www.yoyozone.com
Of interest... Over the years, yo-yo manufacturers have explored numerous ways to address "Yo-Yo Finger"—the discomfort caused by prolonged use of a yo-yo string wrapped around the middle finger. Since the early 1980s, numerous innovative solutions have emerged on the market: