well i found one for $25 and i found out later that 3/4 is the same as 19mm. but thanks anyways, 19mm is the size of the spark plugs on my car

 

Ummm.. I'd take that shit back... They ARE the same for all practical purposes.

19 Millimeters equals 0.748031 Inches
.75 Inches equals 19.05 Millimeters

With the exception that 3/4 will always work on 19mm but depending on tollerances, 19mm will be SNUG or TIGHT on 3/4.