The Duncan-branded "Yo-tility holster" was a three-in-one tool that let you hang a single yo-yo from a belt or belt loop, and cut yo-yo string using the built-in cutting blade. The holster also included a ball bearing removal tool that worked if your yo-yo used a size C bearing (which many yo-yos use today). However, if your yo-yo used a size A bearing--which some Duncan models used--you had to resort to other means to remove the bearing.
The limiting nature of the bearing removal tool and the size of the elastic loop that held your yo-yo are the reasons why the packaging says, "Can be use with most yo-yos!".
