My Godlberg Skylark 70 has the OS .75 AX which has an APC 14-6 prop. The reason is that it is what I had and that's what I used. It works, so I leave it alone... if it ain't broke, don't fix it. But, there are so many different sizes and manufacturers that you can try any of them in your range and find at least one that will work out. As Minnflyer said, it just depends on what you wish to do with your aircraft.