Quick answer

Test-fit each 107 Upgrade Parts limb piece on the bare RG Zaku frame before final assembly, trim or sand only where contact occurs, and pose the finished limb through its full range once before locking it into a display stance.

Why limb upgrades need a dry-fit first

RG Zaku limbs are built around a small inner frame, and add-on parts change how much material sits around the joints. A dry fit on the unpainted frame shows you exactly where the new piece contacts plastic, so you can adjust the part rather than force the joint.

Work on one limb at a time. If you fit all four limbs before checking movement, a tight shoulder or knee can hide until the model is fully assembled and harder to disassemble.

When to skip the upgrade or change your plan

If a limb piece needs heavy sanding to clear the joint, stop and reconsider. Aggressive trimming can weaken the part or remove detail you wanted, and it may not be reversible.

The 107 set is a special order with a 4-5 week lead time, so check your kit and your patience before committing. If you need parts quickly for a repair, this is not a fast fix.

Step-by-step fitting and posing process

  1. Build the bare limb first: Assemble the RG Zaku arm or leg without the upgrade parts and move every joint through its range. Note any stiff spots or loose connections before adding anything. If the bare joint is already tight or loose, fix that first; upgrades will only make it worse.
  2. Dry-fit one upgrade piece at a time: Snap or rest the 107 limb part in place without cement or force. Check that it seats flush and does not push against the inner frame. A part that rocks or sits proud is not seated; find the contact point before sanding.
  3. Mark and relieve contact points: Use a pencil to mark where the part rubs, then sand or trim only those spots in small passes. Refit after each pass. Stop as soon as the part seats without pressure; over-sanding loosens the fit.
  4. Check the full range of motion: With the part fitted, bend the elbow or knee slowly to its limit. If the upgrade blocks movement, identify whether the part or the pose is the problem. If the joint cannot reach its normal range, adjust the part rather than forcing the pose.
  5. Pose within the new limits: Choose a display stance the limb can hold without strain. Support heavy weapons or extended arms at the wrist or forearm rather than at the shoulder. A pose that slowly droops means the joint is overloaded; bring the limb closer to the body.
  6. Recheck after paint or topcoat: Paint and clear coats add thickness. After finishing, refit the limb and move the joints again before final display. If a joint tightens after coating, sand the painted contact area lightly rather than forcing it.

Product facts