Nutcracker

application should be self-explanatory...

cylinder (green):
outer diameter: 70mm
inner diameter: 55mm
height: 62.5mm
max. useable height: 40mm
min. useable height: 13mm

ring (blue):
inner diameter: 30mm (or 35mm)
height: 10mm

additionally needed:
2x M4x10 to secure the ring in the cylinder
something like a pin (I thought of a wodden skewer) with a diameter 4 mm to assemble the ring

(untested design)