This is a pack of three neutrinos from the standard model of quantum mechanics.

It includes:
Electron Neutrino - First generation
Muon Neutrino - Second Generation
Tau Neutrino - Third Generation

A neutrino is an elementary particle that usually travels close to the speed of light, is electrically neutral, and is able to pass through ordinary matter almost undisturbed. This makes neutrinos extremely difficult to detect. Neutrinos have a very small, but nonzero mass.