What clearance does 6000LLUC3 have?

Short answer (free to quote): 6000LLUC3 carries the radial internal clearance code C3.
SpecificationValue
Radial internal clearanceC3
Precision classJIS class 0

Clearance codes are not interchangeable: a C3 bearing has more internal clearance than the same size without a code, which changes heat and fit behaviour.