Aikoi Wind Up Racing 4 Mice-Realistic Looking Mice - Set of 4 This package of 4 mice has my cats racing around. Each mouse is about 4.5 inches long [not counting the tail.] They are powered by winding them up. When you release the handle, the mouse runs across the floor and it's tail twirls around Come in 4 mice in the set. Each of these are really fuzzy feeling and pretty cute for a mouse. Simply pull them back and then watch them scurry across the floor. There little tails even move. Your dog, cat and kids were chasing these around Too cute The more quickly on my wood floor or the tile floor but not on carpet. If they hit a wall they will turn and go the other way about 75% of the time. If they don't turn, they simply stop at the wall I'm sure if you were to play with this around an old woman, you'd hear a scream. They do look kind of realistic from a distance. They're easy to use. You just wind up the mouse, and let it run. Little wheels underneath the mice propel them across the floor They'll travel for about 15-20 seconds per wind up, which turns out to be at least 10 feet of distance traveled. (What happens is they travel in straight lines, so they hit the wall, and stop. Or, the cat catches it and it stops.)