US UK EUROPE INTERNAL
DIAMETER
5 J1/2 9.3 15.7mm
6 L1/2 11.9 16.5mm
7 N1/2 14.5 17.3mm
8 P1/2 16.7 18.1mm
9 R1/2 19.3 18.9mm
10 T1/2 21.5 19.8mm