Clock Key Size Chart

Size Swiss American
000 1.75mm 2.0mm
00 2.00mm 2.2mm
0 2.25mm 2.4mm
1 2.50mm 2.6mm
2 2.75mm 2.8mm
3 3.00mm 3.0mm
4 3.25mm 3.2mm
5 3.50mm 3.4mm
6 3.75mm 3.6mm
7 4.00mm 3.8mm
8 4.25mm 4.0mm
9 4.50mm 4.2mm
10 4.75mm 4.4mm
11 5.00mm 4.6mm
12 5.25mm 4.8mm
13 5.50mm 5.0mm
14 5.75mm 5.2mm
15 6.00mm 5.4mm

Measure across one side of the flat to determine size