This is a set of Element Trinity Abec 5 Bearings which includes 8 bearings.
"The ABEC rating system includes grades 1,3,5,7, and 9. The higher the ABEC rating, the tighter the tolerances are, making the bearing a more precision part. High precision and small tolerances are required for bearings to function at very high RPM, in products like high speed routers that must spin at 20 to 30,000 RPM. In an application like this, an ABEC - 7 or 9 bearing rating may be appropriate. However, a skateboard with 54mm wheels turning 20,000 RPM will be traveling about 127 MPH! Since virtually all skating is done under 30 MPH, the realistic maximum RPM your skate bearings will see is about 4700 RPM and probably 90% of skating occurs under 2000 RPM. Thus, very high precision is not required at skating speeds."