I lost my original lock nut wrench when I changed flats, this worked great. Count the serrations on the locknut to make sure you have the correct one. 37/21 was recommended for my car (BMW 550i msport 2008), 35/19 worked. The dealer wanted me to come in to "measure" the locknut so he could order the correct part. Count the splines again, I used a mechanical pencil to slide along the grooves. Count 3-4 times to make sure you get the right number.