The sailfin mollys are rather pretty.They are a little different from regular mollys although they will interbreed. Sailfins are Poecilia Velifera and were originally found in Central America and Mexico and can get 3-1/2 to 4 inches in ideal conditions.
Regular Mollys are Poecilia Sphenops and were originally found in North America and South America from Texas to columbia. and so were one of our native fishes. They can get to 3 inches in ideal conditions.
sorry for the rambling

Just thought it is interesting that they are different, usually the larger fins in most fish are recessive genes and they have been bred until it is a fixed feature (like guppys)
carol