These high quality thread reels feature professional plastic injection molded parts, longer retraction distance, unbreakable tube, glass bead for smooth function, and easy maintenance and repair. Each contains 30 feet of invisible thread and allows you to pull out invisible thread for use and retract it when you're done, saving it for another time. One end of the invisible thread is wound around a center core that automatically winds up the thread for you and the other end is attached to a wax ball. This wax ball makes it easy to find the end of the thread and will stick to just about anything.