There are many accessories you can purchase to keep your YoYo sessions running along nice and smoothly.
Probably the most important accessory is spare YoYo string. YoYo strings degrade fairly quickly and you'll find yourself having to change the string fairly often. But don't panic YoYo strings are cheap and we stock them in bulk packs here at YoYo Yo!
The next most important thing you may want to change on your YoYo is the bearing. Bearings come in different shapes and sizes, and they can be maintained by cleaning and lubing. YoYo lube comes in both thin and thick varieties, for unresponsive and responsive play respectively.
Other accessories include response pads (to change the responsiveness of the YoYo), shims (to widen the YoYo) and replacement axels.