Welcome

these wheels are installed with bearings

the bearing internal diameter is 8mm

WARM TIP:

Dear friend,  thank you for your order. after receing the wheels, if you find the wheel working not well, please try to remove the bearings and install them again.

we test each wheel working well before packing but during the long distance transportation and loading unloading, if two bearings hole and one spacer hole not in the straight line the wheel working not smoothly.

so the solution is

Remove the bearings and reinstall the bearings again.

another solution :