SINGER-Plastic Class 66 Bobbins. 
For Singer models 66; 99; 101; 185; 192; 201; 247; 288; 327; 328; 329; 401; 403; 404; 413; 416; 418; 457; 476; 477; 478; 500; 717; 719; 814; 834; series 6100; 6500 7100 and other drop-in bobbin machines. 
This package contains four measuring 6/16in from top to bottom. Imported.