This product is a set of 5 carbon fiber headset spacers in sizes 3mm, 5mm, 10mm, 15mm, and 20mm, designed for use with 1 1/8" stems on bikes. Made in the United Kingdom, these black spacers are compatible with all types of bikes and are a high-quality component to enhance the performance of your cycling experience. The carbon fiber material provides durability and lightweight construction, making it ideal for riders looking to improve the handling and response of their bike.