Engineered to be lightweight, strong, and durable, the Wolf Tooth Premium Upper Headset gives us smooth steering with minimal maintenance. Constructed from aircraft-grade aluminum in Wolf Tooth's Minnesota shop, this headset uses three levels of sealing to protect bearings from the elements and prolong our headset life. It's compatible with Specialized mountain bikes that use an IS42 upper, and includes a star nut as well as the top cap. Please note that for bikes with carbon steerer tubes, a Wolf Tooth compression plug is required (sold separately). Star nuts pose a risk of damaging carbon steerer tubes.