Here's a couple with the tube in the mount.
Here's one with the mount off, you can see the vinyl dipped
portion on the strap, and the mounting holes for a single screw.
I didn't have a tach or speedo to mount this on.
Pretend the can is your speedo housing. A singe hole in the side,
and a bolt, nut, and lock washer, and you're done. I'll get a shot
of a friends tach with exactly this setup.