its just a 10, i was wanting to prevent case flex..lol
the mini twisters are complete top ends with iron sleeves in them, compared to their counter parts i would think they would be closer to running a cheetah over a cub/serval motor. the mini's are upgradable also, the reed cages and exhaust flanges can be upgraded later on as well as the sleeves for the bigger bores. if the prices are still the same on twister's site its around 1500 starting price to get a mini, so the cost is around the same as getting into a cub motor if your having to buy a head intakes ect.
the only real down side i could see is that they are a little heavier than cub's.
Dont get me wrong either, I have currently a cub motor (stock stroke 68mm bore) and the motor in the pictures above (10mm 75mm bore). Probably soon ill be breaking down the stock stroke motor to build a 4mm dm as well.