Laser Rangefinder

Lasers measure exact distances to the pin or other objects.

Lasers with slope measurement

These products provide players with a distance measurement to the flag that takes into account the change elevation between the ball and the flag stick.

These can be used in practice rounds but are currently not legal in competitions.

There are hybrid devices that are capable of slope measurement but can be visibly disabled by moving a component that makes them legal for use in competition.

For most players this is not  a feature that is needed

Laser

Lasers are excellent for exact distance measurement and are best for short range measurement for approach shots

Hybrids

There are units that provide GPS on a laser