Friendly Robotics manufactuers robotic lawnmowers under the RoboMow brand name. On their website, they list several different models including: RL2000, RM510, RL855, RL555, and RM200.
The RL 850 is the older version of the current RL 855 and it is sold on Amazon.
From the Amazon page for RL 850:
"Powered by exclusive drop-and-go 24-volt batteries, the heavy-duty Robomow RL850 is a 53-centimeter, 21-inch mower/mulching system. With its three blades spinning at 5,800 RPM--double the speed of a typical gas mower--the Robomow RL850 travels across your lawn in a crisscross pattern, covering up to 10,800 square feet on a single charge. Easy to set, the Robomow RL850 delivers a 1.75- to 3.25-inch cut with high-cut blades and a 1.0-2.5-inch cut with low-cut blades.
- Automatic lawnmower mows entirely by itself
- Cuts up to 10,800 square feet in a single charge
- On-board sensor and bumpers to avoid obstacles
- Grasscycles for a healthier, greener lawn that requires less water
- Quiet operation means you can mow day or night "