Class 66 bobbins compatibility compatible with Singer 66 Class top load rotary hook models that use class 66 drop in bobbins verify size 20.45x6x10.72 mm to ensure proper fit before purchasing or installing OEM reference OEM 172336 matches the class 66 clear bobbin profile supports smooth thread winding and steady feed helps reduce bird nesting and improves stitch consistency for daily sewing and practice Material and size transparent plastic bobbins with 20.45 mm outer 6 mm inner and 10.72 mm height smooth edges allow quick visual check of remaining thread and easy insertion into top loading bobbin case Functional uses suitable for winding cotton polyester or embroidery thread supports garment repair hemming quilting applique and craft projects practical for DIY users students beginners and hobby sewists Application scenarios ideal for home classrooms small studios and travel kits keep pre wound bobbins organized to switch colors quickly during quilting patchwork mending and light upholstery tasks, Manufacturer: YINETTECH