To ride with a partner you have to be at least 42 inches. There was not an age requirement. They are very strict about this. My DD must have been 41.99 inches. The bar was touching the top of her head, but they said if you can stand under the bar, you are too short. I tried saying that her head was meeting the line, but the CM said there were 2 cameras watching him and he had to go by those rules. She was very sad, but I know they are just trying to keep everyone safe. To ride by yourself, I'm pretty sure you have to be 54 inches, I'm not 100% on that though.