Allows Zeepro Zim to hold more filament than its physical size would appear to allow. You can utilize full 1Kg spools, along with smaller 1lb rolls. Requires removing a couple of parts, and will effectively bypass the cartridge mechanism.What you'll need for dual spools: 11/64" drill bit. 5/32" drill bit. 2x 3/4" #8 machine screws. 2x #8 lock nut. 2x 5/8" metal screws. 2x ~1.5' PTFE teflon tubing 4mm OD X 2mm ID. 2 sets of these parts. Fast preset works fine for this. There are a couple of overhangs on the hook bracket, so be sure support is enabled if using some other preset. The holes are intentionally slightly smaller than needed so that they can be drilled out for a more accurate fit. None of the screws are tighened all the way, just snug but where the arms still move freely as the head moves. Drill both holes in the longer (50mm) arm with a 11/64" drill bit. This will allow a #8 machine screw joining the arms to move freely. Drill the holes in the top of the large back hook bracket with 5/32" bit. Note it is not required to drill this all the way through assuming a shorter screw is used. A 5/8" #8 sheet metal screw can be used here to connect the long arm to the back plate. Drill one hole in the shorter (30mm) arm with 11/64", and the other with 5/32". The smaller hole is to accept the PTFE teflon tube with a friction fit. It should be tight. The larger hole is for the #8 machine screw that connects to the long arm. See pictures and assemble the bracket arm as shown. First slide the spool holder down the hook bracket. Push it onto the tab at the bottom until it snaps into place. Be sure the spool holder is on the correct side. It is a tight fit and may break attempting to removing the spool holder once it is snapped into place. Use a 5/8" #8 sheet metal screw for the longer arm attachment to the spool holder plate, and work this slowly to create threads. The PLA is weakest at the hooks where this holes are, forcing the screw may crack the PLA. Go slowly. Leave the screw slightly loose such that the long arm moves freely. Use the 3/4" #8 machine screw and locknut to hold the short arm to the long arm. The short arm had a larger hole and a smaller hole. Use the large one, and leave the lock nut slightly loose such that the small arm moves freely. Remove the teflon tube from the extruder by pressing on the compression fitting black ring and pulling it out. See the zim support website FAQ on removing/replacing teflon tubes for more information if needed. Press fit the new teflon tube into the smaller hole you made on the shorter (30mm) arm. It should be a tight fit. It doesn't have to go all the way through, just fit in enough such that it is snug. There will be a slight amount of tension and compression on this fitting during operation. Insert the other end of the teflon tube in the extruder on the appropriate side. It should be inserted 27.5 mm (see zim support FAQ on removing/replacing teflon tube if needed). Unplug the lower stepper filament micro-switches (disconnect the connectors). This makes the Zim think there is filament in the tube. Thanks to Scientist for this tip! Also you can remove the black plastic shield that forces the wiring harness and original PTFE tubing down the back if you like. It seems to allow the red/black wiring bundle to move freely and reduce stress (see pictures). This piece is only held in by some double stick tape and is not attached to the gantry, despite what it may appear when you first tug on it. You can always put it back in if you miss it. Loading and Priming: You may actually find this easier than the original loading procedure, but it requires feeding the filament into the extruder stepper by hand. Fortunately the filament is easy to feed now with a very short length of PTFE tubing and direct access to the spools. Ensure you have a refillable spool in a cartridge holder, or simply the back plate from a cartridge (see this thing http://www.thingiverse.com/thing:611463 to make a clip for a cartridge base plate). Push filament most of the way through the tube to the extruder, but not into the extruder head yet. Select "prime" from the manage my Zim cartridge menu. The "load" option will be missing because we bypassed the microswitch down in the lower compartment, so the Zim will think the filament is already loaded. Once the extruder is heated and the extruder starts to feed, push the filament the rest of the way so it grabs in the extruder. You should see it start extruding, done! Print as usual. You have about 4-5 times as much filament as a stock Zim cartridge when using a single 1Kg spool. You may want to go to the http://zim/cartridge/left or http://zim/cartridge/right menu and set the filament color and start length. The Zim software only allows setting this value up to 200 meters. There is about 400 meters on a 1Kg spool of 1.75mm filament. You will have to reset it at the halfway point to track to last 200 meters. When swapping spools, I usually jot down the approximate amount left on the side of the spool so I can reset it when I reload that spool.