JMac - MDi-co

ST-6 Skeletonized Tube

(11 Reviews)
Current Stock:
2.90 Ounces
SBA3 Brace

(S)keletonized(T)ube(6)inches long and 6 positions - NO MOUNT INCLUDED

This M4 tube adapter replaces the standard buffer tube to ensure the stock folds as flat as possible! (With proper folding adapter)

Fits most M4 style stocks/braces 

Lightweight and Rigid

  • Integrated QD Sling Sockers
  • 6” Length
  • 6 positions 
  • Compatible with SIG folding mechanisms
  • 7075 T6 Aluminum
  • Type III Hardcoat Anodized

Requires a mount or folding mech to install!

Attaching a stock to a pistol makes it an SBR and requires NFA approval. You are responsible for knowing and following your local/state/federal laws!

JMac Customs LLC is not responsible for the end users misuse  of our products.

Reviews (11)


Written by T.I.P on Mar 11th 2022

Wanted to buy this and the Folding Stock/Brace Mount for 4.5mm Folding AKs. Will have to wait. Other than that, this is the first item to fully secure a SB tactical SBA3 with *Zero Wobble*. Machined piece with anodizing. Does the job it supposed to. Wish it came with inch/lbs torque recommendations.


Written by Clinton on Feb 7th 2022

The ST-6 is fantastic... not only is it aesthetically pleasing,it's rugged. The finish is great and the machine work is fantastic...The extra QD socket is also a bonus. One other thing is the shape of it on my check seems to fit better into my check bone pocket where standard buffer tube seems to be larger and not as comfortable. It fits well on my kp9, sig canebrake, M85 and anything else that does not require a standard buffer tube assembly.


Written by Steven Perkins on May 31st 2021

Awesome product, mounted right up to my Sig MCX and fit a SB3 brace perfect!

Great Stock

Written by Clint Blumenberg on May 18th 2021

Lightweight, slick looking, and goes great on my MCX. It can be a little stiff to adjust positions, but I don't move my stock much anyway, so not a big deal. Great piece!

St6 skeletonized buffer

Written by Ryan watkins on Apr 23rd 2021

Paired perfectly with my arsenal adapter. Beautiful fit and finish. Absolutely no complaints


Written by Steven on Apr 12th 2021

Bought this to replace the stock pistol brace with a Magpul stock after I SBR'd an MCX pistol but still wanted the foldability of OEM stocks. Unscrewed the pistol brace from the 1913 adapter and installed the ST-6. Magpul CTR fits perfectly and now I have the best of both worlds - foldable stock but with my own choice of buttstock!


Written by Christopher Nutter on Dec 29th 2020

Seems like a well made quality product. Fitment and finishing is superb. Looking forward to seeing how it looks on my Arsenal 104rf.


Written by David on Nov 28th 2020

This was the perfect combo with the 1913 mech and a sba3 brace. Wow! It looks amazing and I have no complaints.

ST-6 adapter

Written by Todd on Sep 19th 2020

Ok, wow. This product exceded my expectations big time. I already had a Sig folder on my AMD with JMac adapter so i didnt order the ST-6 with one. Hey, do yourself a favor and order it with one. Trying to take out the Sig installed bolt was tuff. But once i got it on it is perfect! The Magpul M4 stock i used doesnt rattle on the ST-6 and lays almost flat against the receiver when folded. Top notch product

Great option for AR stocks/braces

Written by Michael on Aug 30th 2020

Picked this up to put on my Galil ACE. Paired it with the Sig folding mech. The JMac tube looks better on the rifle compared to an AR buffer tube. Excellent machining and fit. Stock fits perfectly on the tube.

Amazing Brace mount

Written by Nathan on Aug 26th 2020

I ordered this with the Sig folding mechanism for an MCX and used it with a SBA3 brace. This this is infinitely better option that the annoying spinning on the factory Sig brace. Solidly built, locks up amazingly, cannot recommend enough!

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