This nipple is 1/4" MPT X 17" MPT (Male Pipe Thread). This is often used to attach two air manifolds together or for other applications where you need to join two Female 1/4 FPT parts together. It is one inch long.
WARNING: This product can expose you to lead, which is known to the state of California to cause cancer, birth defects and other reproductive harm. For more information go to: www.P65Warnings.ca.gov.