Viper

VIPER is the smallest, lightest, and most compact device in its class, measuring at only 254 grams (without battery). Its sophisticated low-profile clip-on design eliminates the need to remove your day sighting equipment since the device mounts directly in line with a standard daytime rifle scopes without the need of any tools. Most importantly, you do not need to re-zero the rifle every time you change the sight, which means point of impact always stays the same.