The 737 MAX only has three types. They are the 737 MAX 7, 737 MAX 8 and 737 MAX 9. The 737 MAX 7 will replace the 737-700, the 737 MAX 8 will replace the 737-800 and the 737 MAX 9 will replace the 737-900ER. The -700, -800 and -900ER sold the most out of the 737 Next Generation family.