The OS1 (short for Off-String 1) was YoYoJam's first ever offstring yo-yo, prior to the introduction of the popular Aquarius.

It was a limited release produced in 2001, having first debuted at Worlds. It is a plastic yo-yo with soft rubber shells that formed a Butterfly-shaped body profile. It also features starburst response, and the usual B-sized bearing.

A glow-in-the-dark variation, as well as an "Americana" edition, were also produced.

The OS1 was also sold in Japan.



  • It uses the same kind of side cap design on one side as the Jam.
  • A lot has changed the last 14 years since the OS1's release, and as technology improved, so had YoYoJam's offstring models. While the OS1 was YoYoJam's first offstring yo-yo, the Fiesta TRES of 2015 is their last ever one, as of the December 17th, 2015 Facebook announcement of the company closing its doors.

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