Summary

It seems no one makes Minecraft piston, so I created this functional one.

All measures are precisely in accord with in the game. Inside there are stopping blocks in each section so it won't be pulled apart.
(the piston is a two section piston in the new version Minecraft, otherwise it won't extend to 1 cube tall)

My first printing was successful but a little bit too tight, and I have thus increase the gap a little bit and made very small inside filet. Sanding a little bit on the contact surfaces after printing, and then assemble from the bottom. Glue the top and base cover if you like.

I printed at 20%, I think 15% would still work but no less.

Hope you like it.