while messing with redstone i gave myself the challenge of making a more compact way of the way i build double piston extenders.

what you need:
6 of any block

2 pistons (one must be sticky, it goes on the bottom)

1 redstone repeater (set it to 2 ticks)

4 redstone

then copy the images :)

enjoy!

(i did not count the lever too the block total)