Do not default your engineering drawings to TG2 or TG3 unless absolutely necessary. Tightening tolerances exponentially increases mold manufacturing costs and cycle times.
The standard classifies tolerances into , typically ranging from TG1 to TG9. TG6 is the most common baseline for commercial plastic parts. Nominal Dimension (mm) TG4 (Precision) TG6 (General) TG8 (Coarse) iso 20457 tolerance table pdf