The Singer Notions 6543 Transparent Plastic Class 15J Bobbins come in a pack of 12 and are designed for use with Singer sewing machines. These bobbins are made of durable plastic and are transparent in design, making it easy to see the thread inside. With a height of .53 inches and a weight of 0.1500000, these bobbins are lightweight and compact for easy handling and storage. Perfect for sewing enthusiasts looking for reliable and efficient bobbin replacements.