Just measure the plastic spinner you have on it and buy the same size or one you think looks cool. Most spinners you buy need to have the blade section opened up more anyway using A Dremel with A cut off wheel or grinder. The second number is the pitch of the prop, no need for me to get into the way they measure it for you. An easy way to remember your pitch selection is this: shorter prop bigger pitch= more speed with less torque. Longer prop with less pitch= less speed but more torque. I fly stunt planes so I use the longer props with the smaller pitch to slow my planes down but pull the plane harder. It makes for shorter take offs too. I buy A bunch or props of different sizes and test them on my plane to see what works for ME the best. Notice that ME thing, another pilot may like the same plane with A different prop A bunch better. That sort of kills the question I see all the time about what size prop with this engine on this plane. Any number of props will fly the plane very well. Yesterday I broke the only 14X6 APC prop I had, today I'm going to fly the same plane with some odd ball prop I had that will work on that engine. No idea at all if I'm going to like the way it fly's the plane but I know the plane will fly with it. Question, are you saying you have no club close by that may have an instructor to help you out? Most clubs have someone that will and most instructors have A trainer with A buddy box to get you going on the real thing. Even if someone set you up on A buddy box with your Laser you would be ahead of the game.