Use the bobbin style named in your machine manual. Singer separates transparent Class 15, Class 15J, metal Class 15 and Class 66 bobbins and warns against substituting those styles.
Compare an unwound original with a replacement from the side as well as above. A bobbin that drops into the holder can still have the wrong height or profile.
Visible differences help you sort bobbins
Singer describes transparent Class 15 bobbins as flat on top and bottom. Class 15J has slightly curved faces and is shorter. These observations help separate loose bobbins; they do not replace the manual’s required class.
| Bobbin | Useful distinction | Decision |
|---|---|---|
| Singer transparent Class 15 | Flat top and bottom | Keep separate from metal Class 15 and 15J |
| Singer Class 15J | Slightly curved faces | Do not substitute for transparent Class 15 |
| Brother SA156 | Clear plastic, 7/16 inch deep | Use Brother’s exact model list |
| Janome 102261103 | Clear bobbin with J marking | Use Janome’s fit list and exclusions |
Material is part of the specification
Brother excludes metal bobbins in the machines covered by its SA156 support answer. Do not turn a broad marketplace label such as “Class 15 compatible” into permission to use any material.
Separate damaged and unidentified bobbins
Discard chipped or distorted bobbins. Keep unidentified loose bobbins apart from the ones assigned to a machine. Labelling a storage box with the machine and replacement reference prevents the same comparison at every colour change.
