I bought this about 6-7 years ago at an electronics store that had a permanent course. At the time, my three elementary school-aged daughters and I each assembled and raced our cars. For a while, we took them out and raced them every time we went to the mall where the store was located, but we gradually stopped playing with them. They were completely forgotten, but I found them while cleaning up. The machines are completely stock, with no modifications. No separately sold parts have been installed. My elementary school-aged daughters assembled the cars and applied the body stickers. The store's course was free and always empty, so I think we raced for at least an hour each time. They've been stored in their boxes in a room-temperature place for the past 4-5 years. I put in batteries and turned on the switch, and they ran in four-wheel drive without a problem. Please consider them for parts, etc.