Sillymike
I actually recommend the Aluminum. They are Aircraft grade anodized and have a very hard surface finish.
The PIIC clamp-on is Aluminum also.
Seriously, he uses an excellent T6 grade bar stock for them.
Speckfire
you already have a scope mount. you only need the PII diopter that attaches to the scopemount and your're ready to rock, unless you need an extra for your second K31?