To fill a gearbox with grease can be messy scooping out of a container. I tried a grease cartridge but found it worse as I had to cut it open to get all the grease out.So I designed a simple plunger that I could push down the open end and dispense the grease directly into the gearbox.I made the piston out of a fluo colour in the hope it wouldnt get accidently left in a cartridge and thrown out. I made four small channels in its face to make sure every last bit of grease could get away from the edges at the very end and into the centre to wipe off into the gearbox.The handle i made from some 12mm tube I already had. Conduit would work as well. I glued the two ends on with Tetra after cutting the tube to a sutable length.The small end is inserted into the piston and turned 90degrees so its engaged with the slots in the two bulkheads.The small end of the handle was printed at 20mm fill. However, the handle I printed at 50% fill as the first attempt at 20% wasn't strong enough when withdrawing the piston back out of the cartridge.