This plaything is an ecofriendly RoboMower RL850. It runs by the green button on the unit. Powered by battery, this three-blade 21-inch powerful cutting system travels on the lawn in a systematic criss-cross pattern covering the lawn several times so that the grass is cut from every angles. To drive it well, you need a special electric perimeter wire around your lawn, the RoboMower has a special senor to keep it confined to the electronic fence. However, you need to recharge it for 24 hours to keep it well. You can have best of it on the surface that has less than a 15° incline. Those not sure of a docking system, RL850 is worth having for $1,175.99, at Vacation Gadgets.