Maccari came out with these in the mid 80's for guys who wanted to button their piston or compression tube but had no tools.
You get 6 buttons
They run about .250" OD.
Simple Installation.
Degrease piston or comp tube etc. ( Brown button side too)- rubbing alcohol works fine
Use instant glue only like Krazy Glue Etc.
Glue Brown side down- full coverage of the button.
Maroon side is the side you see when installed.
Hold 20-30 seconds until glued. Do not over glue.
It is no good to set a button on a pile of glue- use as little as possible.
Gel instant glue sometimes is too thick.
Sand with 220-320 grit to size required- Fitting it till its snug or somewhat less.
If you have a buffer-use it to size-If not hand sand Maroon side as above.
Works best with wet edge- apply moly or clear tar if its a comp tube.
Thats it- No drilling or milling. Just degrease, glue, hold, fit, and its ready to use.
I put 6 buttons on a .22 R1 and gave up looking for wear after 20K shots. So they last really a long time or forever.