If you're looking at this piece you have probably broken the brittle plastic nipple off of your fuel feed assemble on your BMW N47, N57 or B57 engine.  This piece is an aluminum replacement, so you ONLY need to replace this piece instead of the entire fuel hose assemble as the original plastic Tee is not available separately.  

Fits the following US BMW Diesel applications.  Will fit many other European models as well.  

13537810786 - N47 - F30 328D, F31, X3

13537823400 - N57 740LD, X5 F15, F10 535D