This motor will be optimized for a 4" light to medium weight prop. 4" is still a bit of a bastard size but we do expect it to grow with the prevalence of the DJI system coupled with drastically simplified electronics. This motor very well could end up being the same motor as the cinewhoop motor but we're testing two motors specifically for 4" as well just to make sure.
Four inch is a funny size that you can build with 5" electronics and super meaty props or you can build with micro components and light props. To us, 4" flies far closer to 3" than it does to 5" so we're taking the micro route and expecting the scale up of the recently excellent micro electronics to be more popular than trying to squeeze 5" electronics into a smaller package. With that being said, the 4" motor will not be intended for ANY bull-nose props. In our opinion, if you're planning on running bull nose props in the 4" size, what you're really looking for is a 5".