For the record, these are the easiest cartridges to refill! The only "problem" I've had refilling them is trying to seal up the hole I made to inject the ink. I've tried electrical tape, plugs, screws, hot glue, but they all seem to not seal all the way 100% of the time, or leave a residue (elec. tape). I've had the "best" success with the plasti-tac stuff, but sometimes it pushes / falls into the ink tank, or wicks ink out and makes a mess. I'm doing some tests with a syringe I modified. I plugged the exit hole and drilled a hole into the side of the syringe wall. I've been inserting different plugging solutions to see which ones work best. I put the subject to be tested onto or in the hole in the syringe and I push or pull on the plunger to see what happens. Here's what I've found so far from best to worst: 1) Plasti-tac: seals well, but pieces can get stuck and fall into the tank 2) Hot glue: sometime it seals, but sometimes it doesn't and it's hard to tell the difference. Also it can be hard to remove for the next refill 3) Electrical tape: sticky residue, doesn't always seal, especially if there is any moisture / ink present. 4) Screws: Sealed great at first, but subsequent times had progressively worse sealing power. 5) Plugs: Didn't get a very good seal most of the time. I've settled on using the cartridges from www.alotofthings.com which have a hole / plug combination that actually works pretty well. Tape is needed on top of the plug to ensure a air tight seal. UPDATE: I've been experimenting with the cloth duct tape and am so far VERY impressed with the results. I've got some on a few different cartridges to test the seal and to see if any residue is left after a while. I'll keep you posted.