Slotless BLDC motors are available in long and short versions with different output powers and different winding types. MOONS' micromotor system includes slotless motors with gearboxes, encoders and drivers.
For these motors, ironless windings are used which helps to provide high torque and power density in a very compact motor size. These products are cogging-free, and provide an operating life of up to 20,000 hours. Moons' provides 13mm, 16mm, and 22mm diameter products that fit many applications.
https://www.ipcmotors.com/ipcproduct/motori-slotless-brushless-dc/