They work with Electric cone winders. There are mages showing the notch and the purpose of the notch. One is of a close-up of putting the pigtail in
Cardboard Cones for Crafts, Winding Yarn, Lot of 4, Works with Cone Winders
Cardboard Craft Cones FOR SALE! - PicClick
Other Needlecraft Supplies, Needlecrafts & Yarn, Crafts - PicClick
They are all in excellent condition.
Cardboard Cones for Crafts, Winding Yarn, Lot of 4, Works with Cone Winders
Keep your yard clean and organized with these empty cardboard yarn cones from The Woolery! These cardboard thread cones come in packs of 25, 50, and
Cardboard Yarn Cones
Winding yarn on a cardboard core
Cardboard Cone – Tufting Box
Cardboard Craft Cones FOR SALE! - PicClick
Cardboard Yarn Cones
Winding yarn on a cardboard core