An accelerator ring or Precursor ring is a device used in the Jak and Daxter series. Some rings will accelerate the velocity of an object when passed through it (accelerator rings) while some do not serve any purpose other than objective points used in vehicle challenges (Precursor rings).
Precursor rings first made an appearance in The Precursor Legacy during the missions "Navigate the purple Precursor rings" and "Navigate the blue Precursor rings", during which Jak had to fly the A-Grav Zoomer through them in a consecutive order before time expired (indicated with the sound of a ticking clock). When passed through these, the rings would expand and dissolve, then disappear.
Precursor rings again appeared in Jak II in side missions. Same as in The Precursor Legacy, these rings did not accelerate the vehicle passed through it. However, during the mission "Beat Erol in race challenge", Jak and Erol flew through accelerator rings in Haven City using zoomers, and these rings did in fact accelerate the vehicle.
Accelerator rings again appeared in Jak 3 throughout Spargus and the Wasteland. Oracle totems (and in one mission, Precursor Monks) would give Jak Precursor ring challenges using leaper lizards to earn Precursor orbs (or in the case of the Monk race, a light eco crystal). In the Wasteland, Jak had to use accelerator rings to keep the monk glider airborne. These accelerator rings had a Precursor metal-crafted rim around the circumference of the ring, and some were deactivated and had to be shot in order to activate.
Accelerator rings are usually purple, blue, or red in color, and consist of cloud-like lasers in the form of a circle. The inner detail of these rings vary vastly per game and purpose, though usually either consist of a translucent holographic substance, or smaller rings travelling towards the center of the circle.
In most accelerator rings, a gray/disabled accelerator ring will appear in front of the currently active accelerator ring. This will show if a previous accelerator ring has not been passed through yet.