The Speed Chuck pump head threads directly on to the Presta end of a Lezyne Flip Chuck pump head and accomplishes two things. First, it allows you to slip the head onto a valve stem instead of threading it on like the Flip Chuck head. Second, it's distinct 90° angled profile works with disc wheels, not just standard wheels. This CNC'd and polished pump head is deeper and more durable than the plastic version that is included with all Lezyne floor pumps. And if you have an older pump where the Speed Chuck wasn't included, here goes.