What's the difference between Nerf Elite, Rival, and Hyper?

Elite uses standard foam darts and is the mainstream line for kids and casual play. Rival uses high-density foam balls ("Accu-Rounds") and is positioned as the higher-velocity, more accurate competitive line — reviewers note better out-of-box performance but bulkier blasters and more expensive ammo. Hyper uses smaller high-velocity rounds. Of the three, Rival has the strongest accuracy reputation across the reviewers we read.