I have 8 MK 3644/24mm 6mm motors for sale. These motors are 6S compatible. Because of weight issues these motors are ideal for copters flying with 1 6S battery (not two) and for up all weights of about 5.5kg to 8KG. In my opinion I would rate these motors a little less output than the 4012's although MK rates them the same. These motors are made for 13 to 15 inch props. 16 inch props are not suggested. I only made 4 flights with them, good condition. I wanted to try them on my 10.5kg copter but that weight was just a little to much. Will ship anywhere. I paid $89.each. I would like $300 US for all 8. If interested please email designedavsolutioons@verizon.net thanks Dave