I used this on my C8 when imaging in Fastar mode. If the
focus knob is the same on a C9.25 or C11 it should also work
for those-- but I am not sure. The micrometer is a Vishay high
quality 4 digit unit. with over sized focus knob. The mounting
bracket is machined aluminum. See pic below.
Has installation instructions, and is easy to install.
$50 plus shipping.