KJ bearing is a specialized manufacturer of airsoft gun bearings. It makes in metric size.

6mm Bearings
6mm ABEC-3 or better steel bearings for all chassis that take 6mm bearings or bushings. These bearings come with metal shields, a premium light grease and are ready to install.
3x6x2.5mm (MF63ZZ)

7mm Bearings
7mm ABEC-3 or better steel bearings for all chassis that take 7mm bearings or bushings. These bearings come with metal shields, a premium light grease and are ready to install.
3x7x3mm (F683ZZ)

8mm Bearings
8mm ABEC-3 or better steel bearings for all chassis that take 8mm bearings or bushings. These bearings come with metal shields, a premium light grease and are ready to install.
3x8x3mm (MF83ZZ)