4mm Allen Nut Hot Rod Truss Rod

  • 97 Reviews
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12-1/4" overall length

Item # 2550
In stock, ready to ship!


6 or more $13.74
12 or more $12.95

14-1/4" overall length

Item # 2551
In stock, ready to ship!


6 or more $13.91
12 or more $13.11

18" overall length

Item # 2552
In stock, ready to ship!


6 or more $14.78
12 or more $13.93

24" overall length

Item # 2553
In stock, ready to ship!


6 or more $18.26
12 or more $17.21
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4mm Allen Nut Hot Rod Truss Rod

A smaller 4mm (5/32") Allen nut for most instruments. Smooth two-way action corrects upbow and backbow, giving complete control over the neck.

Easy to install. The Hot Rod® fits in a straight channel. For proper operation, this truss rod must be installed so that the active rod (the rod with the adjustment nut) is below the passive rod. A wooden filler stick is not required.

Smooth 2-way action with superior strength for stubborn necks.
Our Hot Rod neck adjustment system features twin rods in threaded brass collars. The stainless steel active rod turns for smooth neck alignment, with 2-way action to correct upbow and backbow.

The Hot Rod requires an access cavity for the adjustment nut, and a straight 7/32"-wide x 7/16"-deep slot (measured from the bottom of the fretboard) for installation.

Pick the Hot Rod Truss Rod size you'll need:
(overall length includes the nut)

Resonator guitar
Acoustic guitar with 12th fret at the body
Acoustic guitar with 14th fret at the body
Electric guitar

We've designed the Router Bit for Hot Rod Truss Rods especially for routing your neck to fit our truss rods.

Product Instructions

Hot Rod Adjustable Truss Rods

Installation and adjustment instructions for Hot Rod Adjustable Truss Rod.

    • Item #
    • Weight
    • 2550
    • 0.197 lbs. (0.09 kg)
    • 2551
    • 0.232 lbs. (0.11 kg)
    • 2552
    • 0.296 lbs. (0.13 kg)
    • 2553
    • 0.385 lbs. (0.17 kg)

Customer Reviews

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  • 4.42 average rating from 97 reviews
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It Broke Again!

(Customer's Reviews)

OK - I had one of these break with the nut shearing off the rod while doing final set-up on the last guitar I built. StewMac was great about sending me a repair kit and they assured me that this issue was not unprecedented, but very rare. I like the design so I decided to take my chances and use one of these again.

Shame on me...The exact same failure happened again!! Looking at a my experience plus a couple of recent reviews with the exact same problem it looks like there was a bad batch from the manufacturer or something.

Stewmac has good stuff and I'll continue using them for a lot of other parts and tools, but I strongly advise that you do not buy this truss rod.


Best I ever used

(Customer's Reviews)

Been using these for over 15 years and never broke one. I produce a dozen acoustic guitars a year, and there's not a better truss rod out there for my guitars.



(Customer's Reviews)

the concept is a great one however i have sheered the nuts off of more than one of these. the metal is soft and what you would expect from a lower quality cast metal vs. a forged one. it would be nice to have a similar product with a detachable nut like the more traditional fender truss rods.

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StewMac PDF Catalog, page 74 See 4mm Allen Nut Hot Rod Truss Rod
on page 74 of our StewMac Catalog PDF

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  • Hot Rod® is a registered trademark of Stewart-MacDonald Manufacturing Company, Inc.