KV-4/2 tactical switch was designed for simultaneous control of  LED flashlight 'Klesch 2' and Aiming laser Perst-4.Note*If you have Perst-4 manufactured before January of 2020, customer needs KV-4/2 ,but if customers buying it for a new Perst, KV-4/2 will not be compatible. Perst-4 made after January of 2020 are compatible only with KV-4/2U