The O-Ring on the double-strand LARGE JERK-EASE has been properly secured during assembly and is designed so that it will never come off while attached to your dog's leash.
However, the O-ring on the original large Jerk-Ease occasionally came loose during shipping and handling and was difficult to reattach. In April 2017, we made a design change that fully resolves this problem.
If you purchased your large Jerk-Ease prior to that time, and if the O-ring on your large Jerk-Ease came loose during shipping and handling, or at any other time, please email us and we will resolve the issue to your complete satisfaction. Thank you!