HT Poly Backing Thread
A fine thread for an unobtrusive stitch - now used extensively for Machine Embroidery bobbin fill but was originally designed for industry as Blind Hemming Thread and adopted for Felling & Lockstitch - super on Nets and Bridal Wear.
Ideal for Embroidery Bobbin Fill as the fineness of the thread ensures there is no bunching on the back of your work. This also makes it ideal for high density stitched designs as again there isn't an unnecessary build up of thread under your work.
Technically referred to as HT Polyester
Threads In Focus - Learn More
If you are interested in learning more about HT Poly Embroidery Backing Thread, take a look at the article: 'Threads In Focus - Edition 7: HT Poly Backing Thread'. Created by Christine the article focuses on the threads production, uses & properties.