Actually, depending on how old the vehicle is, it may truly be a 19/32 hex head on an SAE thread bolt. I have both a 19/32 socket and a 17/32 - 19/32 open end wrench that were commonly used on some of the older cars for exhaust manifold and some starter bolts. These cars were American made and came out before there were any metric fasteners on US built vehicles. No problem using a 15mm obviously, but when I bought the 19/32 stuff, I had no intentions of working on the foreign cars, so I had very few metric tools.
Chris