Ok I have a 2717 and a 2719 my whip really liked the 2717 better then a 2716/2 20 running a 27 tiger king.Still needs a little more break in ran 5 times about 30 oz of fuel so far.
There is a easy way to remember this. In the ABC line on the two blades .50 bar and .38 bar props, the .50 are always even pitch numbers like 1.4, 1.6, 1.8 ect. On the .38 props it is odd numbers like 1.5, 1.7, 1.9.