I've also never used a 20, 23, 25, or 26 nor had any need for one.

Some of the odd or rare metric sizes we think we need are actually on inch-size hardware. The 240 does use some.

For instance, the drain plug is 1"; actual size 25.34mm across flats. It has threads 3/4 x 16.

Seat belt hardware is inch-sized. That 16 we grab is probably to loosen a 5/8 head bolt. Also in the drive train back of the transmission, the driveshaft flange bolts are 3/8-24 NF with inch heads -- I have to remember to take my 9/16 under there. Same with the Dana rear end. Inches. Some earlier shifter pans are bolted with 1/4-28 NF hardware. Looks like a 10 at first glance; your 11 will work on the 7/16" bolt heads.

There are more, I'm sure. Maybe some of us can recall them.

This comparison I drew up helps me remember which wrench to use when the head is mangled by rust and heat and I need to downsize -- before giving up and using the flamewrench, where one size fits all, of course: wrenchBuddy.gif
--
Art Benstein near Baltimore

You may be only one person in the world, but you may also be the world to one person.