Today there are 4 A versions, the A, A2, A3, and Pro Model (A4). There's also the AW, the basic A with a wheelie-bar, the AW125, which has 125mm wheels and an extended deck, and the Cruiser Scooter, which has the largest wheels (but no 140mm replacement wheels are available) and a wooden deck.
Freestyle scooter riding is a growing sport in not only the US but places like Australia ,France and Japan. Due to the rough demands of trick riding, people often reinforce most of the scooter to withstand impacts and high force. In 2004, Razor released the Pro (A4) model scooter, modelled after the discontinued B model scooter. This scooter is preferred by most freestyle riders because of its bigger size and added strength. The Pro Model built upon the strengths of the B model to become the strongest freestyle scooter released.
Freestyle scootering has a moderately large niche market of riders due to the quick learning curve and many easy "beginner" tricks, as well as the relative low starting cost ($45-$60 for scooter and basic modifications). They have been criticised, however, by BMXers and skaters for crowding up skateparks.