I agree with most of these guys, find a nice 2 stroke 125. The numberss are the engine displacement, you choose the brand. If the #s are fallowed by letters it will represent model, such as: MXC = Track set up, EXC is Trail/Enduro. Not huge differances but gives you an option to get a bike to your riding style. Those are KTM models, all brands are differnt. Two strokes are a good fun bike, with a smaller power band window than a 4 stroke. They can be cheaper to fix if you have a newer model, but if you get a model that is more than 5 years old parts are harder to come buy and will get more pricey as it ages. It is all up to your budget. Make a decision based on your bank account. A 125 will be a fun bike with good power, if you want to get a bike to grow into look for the 250 sizes.