1.5y/f = 1.5 turn wye wind finned

1.5y/s = 1.5 turn wye wind smooth

2.5d/f = 2.5 turn delta wind finned

etc...

If you are looking to upgrade from an 8XL, you could be looking at the 1515 2.5d or the 1512 3d. I just mention these because they are close to the same kv rating as the 8XL. I got a 1512 1.5Y for my truggy and the 1512 is definitely not lacking in power and it runs much cooler than the Feigao.