Photon Micro-Light III Key-Ring w/ Switch, Yellow. The Photon III uses an integrated circuit to provide a push-on/push-off operation. Holding down the button will cycle the light through its 7 different modes: high / medium / low, three different strobe speeds, & an auto-shutoff mode. Squeezing the top half of the button will bypass the circuit and give you full-on brightness regardless of the function you are in. The Photon III is water-resistant & features the same easy battery change compartment as the current Photon I. The Photon III is the same size as the Photon I & Photon II.