Correct wrench size?

[Black Cloud]

I've used a 19mm on the injector tube line nuts before. It seems just a little loose. Is this the correct size wrench that is called out for the nuts?

 

[Billysgoat]

I've used both a 19MM and a 3/4, whichever I lay my hands on first, a lot depends on the brand of wrench as some are closer tolerance than others. BTW, a 19MM and a 3/4 are close enough to make no difference, but 3/4 line wrenches are easier to find

 

[wildmanben]

my snap on 3/4 seems to fit just fine...

 

[dzlfarmboy]

3/4 on injection lines and 11/16 on the banjo bolts for the low pressure fuel system