Our plastic boat shuttle bobbins come in three sizes. The 4" bobbins fit the 9" mini boat shuttles, the 11" boat shuttles, and both double-bobbin boat shuttles; the 5" bobbins fit the 13" boat shuttles; and the 6" bobbins fit the 15" boat shuttles. The bobbins have specially designed ends for trouble-free release of yarn. All plastic bobbins come in packages of 10.