YoYoFactory introduces the break through Hub Stack technology allowing you to literally grab your yo-yo while spinning and hold it in your hand.

Yo-Yos that can be equipped with hub stacks include G5, 888, SuperStar, Genesis +, 44 Special, and Skyline.

However 'Z-Stack attachments' are only recommended for use with the G5 since it is built for stability - however they technically fit on the 888, SuperStar, Genesis +, 44 Special, and Skyline but may affect overall spin quality.