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Plymouth ProMoly Tubing.jpg

ProMoly®: Seamless 4130 Steel Tubing

Trust the Source, Specify ProMoly.

Plymouth Tube Company produces ProMoly® Seamless Alloy 4130 tubing to conform to MIL-T-6736B and AMS-6360.    ProMoly tubing is superior to plain carbon tubing and exceeds the industry specs for 4130 tubing. 


  • Excellent fatigue strength
  • High elongation values
  • Inherent toughness (no weld seam)
  • Predictable, repeatable weldability with minimal distortion


 In addition, using ProMoly offers distinct advantages to frame builders.  The consistency of the OD and wall makes setup easier and minimizes set up variation – a distinct advantage during build season.  And proprietary controls of our annealing process offer welders the benefit of a surface finish with minimal decarburization and oxidation, reducing weld area preparation time.  When choosing a tube for your racing application, trust the source of manufacturing excellence with almost 90 years of experience.   Use Plymouth Tube’s race-proven, industry-approved  ProMoly tubing to bring you across the finish line first on race day!



The preferred ChroMoly material for chassis builders, including:

  • Sprint Car
  • Midget
  • Buggy
  • Dirt Track
  • Rally Car
  • Dragster
  • Motorcycle
  • Tractor Pull
  • Formula
  • Funny Car
  • Stock Car
  • Kart
  • Late Model

ProMoly - 4130 Tubing sizes and specifications:

OD: .125” – 2.250”

OD Tolerance:  +/- .005" (up to 1.500" OD),  to +/- .010" (above 1.500" OD)

Wall Range: 0.02" to 0.250"

Wall Tolerance:  +/- 10% (For ID's Over .500") to +/- 15% (for ID's under .500")

Specifications: AMS-T-6736A,   AMS-6371, AMS -6360, MIL-T-6736B Quality Assurance Certification:  ISO/TS 16949:2012

    • Superior to plain carbon tubing
    • Exceeds the industry specs for 4130 tubing
    • Excellent fatigue strength
    • High elongation values
    • More effecient builds, less set-ups due to consistency of the OD and wall 



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