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
Cyllde eew Cone Winder Yarn Winder Hand Operated Portable Corrosion Resistant Plastic Wool Winder with Detachable Winder Head Swift Yarn Winder needlecraft Yarn Ball Winder
Cardboard Cones for Craft Projects (Package of 12)
Cardboard Yarn Cones, Big Size Old Stock Yarn Cones, Craft Cones, Thread Cones for Tufting Decorations Decoupage SIZE 1
Yarn Winders — CSM Love
These are perfect for winding off yarn so you can put multiple strands of yarn into your tufting machine.One Cardboard Paper Cone for Yarn◆ #1:It
#2 Yarn Cones
Other Needlecraft Supplies, Needlecrafts & Yarn, Crafts - PicClick
Cardboard Cones for Crafts, Winding Yarn, Lot of 75, Works with Cone Winders
Winding yarn on a cardboard core
Yarn Winders — CSM Love
Spare Cone for U-nitt Jumbo Yarn/Wool Ball Winder ML702: White : Arts, Crafts & Sewing
Cardboard Cones for Crafts, Winding Yarn, Lot of 4, Works with Cone Winders
Cardboard Cones for Crafts, Winding Yarn, Lot of 75, Works with Cone Winders
CARDBOARD CONES FOR Crafts, Winding Yarn, Lot of 25, Works with Cone Winders $16.50 - PicClick
Cone Winder - Heavy Duty Ball Winders by NKK
Cardboard Cones for Crafts, Winding Yarn, Lot of 4, Works with Cone Winders