To find the correct blade size please have a look at the engraving on the carriage of your machine. To get precise results the blade size and the carriage size need to match.
Blade Size 10.9 for Machine Diameter 10.0 mm
Blade Size 11.0 for Machine Diameter 10.0 mm
Blade Size 11.4 for Machine Diameter 10.5 mm
Blade Size 11.8 for Machine Diameter 11.0 mm
Blade Size 12.0 for Machine Diameter 11.0 mm
Blade Size 13.0 for Machine Diameter 12.0 mm
Blade Size 13.5 for Machine Diameter 12.5 mm
Blade Size 16.3 for Machine Diameter 15.0 mm