Both the 13x4 and 12.75x3.75 are really noisy though. They do not put much load on the irvine 53 so they get a lot of tip speed noise. They are the best props for 3d-You get the most staic thrust out of them. They also generate a large braking effect at idle so you can do steep aproaches.Use them as long as you don't mind getting infrequent winging complaints from other modellers(especially the scale and warbirders) about the noise! The irvine will also turn 12x6, 12.5x6 and 13x6!
It incredibly robust though. I have had some absolutely dust raising crashes with mine and it still runs absolutely fine with no damage sustained!
Luke