The smallest Laser Rangefinder is the ProMini Range 750 (6/9)

The ProMini Range 750 is the world’s smallest and lightest laser rangefinder at only 145 grams and measures 3.5 x 2.8 x 1.4 inches 

It’s fantastically accurate and ranges from 3-750 yards or 3-700m (simply switch between units as you prefer). It has amazing light-pentration and a super speedy response! This Laser Rangefinder doesn’t have all the technology of many others on the market, but it is a very well reviewed little unit!