First Factory M4 Outer Barrel Shims

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When mixing and matching outer barrels, handguards and receivers there will be differences in dimensional tolerances. Use these shims to eliminate play in the barrel assembly and adjust the timing of free float handguard systems.

Available in 3 thicknesses for fine tuning.

Inner Diameter: 26mm
Outer Diameter: 30mm

  • 0.1mm - 10 pcs
  • 0.3mm - 8 pcs
  • 0.5mm - 6 pcs