Tackform 3.5in DuraLock 20mm Ball-and-Socket Arm, Black Metal — Dual-Socket with Optional Anti-Theft

The Tackform DuraLock 20 Series 3.5" metal arm is a heavy-duty dual 20mm ball-and-socket mounting link in black with an optional anti-theft knob for secure, highly adjustable device positioning.

This compact, precision-machined arm is part of Tackform's 20 Series platform and is engineered to deliver repeatable, strong mounts for phones, GPS units, cameras, and accessories that use the 20mm ball system. Built from metal and finished in matte black, the DuraLock arm offers broad articulation through its dual-socket layout while providing an optional patent-pending anti-theft knob to reduce unwanted removal in exposed environments like motorcycles or side-by-sides.

How much movement and reach will this 3.5" arm give me?

The DuraLock design uses two 20mm sockets to maximize articulation so you can fine-tune pitch, yaw, and roll without compromise. The short 3.5" end-to-end length provides compact reach while still allowing significant adjustment through each ball joint.

• Arm end-to-end length: 3.5"
• Ball center to ball center on the arm: 2.75"
• When combined into a larger Tackform assembly: overall length can reach about 8" with a 7.17" (182 mm) center-to-center span
• Dual-socket layout gives a wider range of tilt and rotation than a single-link arm

Is this compatible with my existing 20mm mounts and accessories?

Yes — the arm is made for the 20mm ball-and-socket ecosystem and fits most components from Bulletpoint, 67 Designs, iBOLT, and other manufacturers that use 20mm balls. It is not compatible with larger 25.4mm (1"/B-sized) balls.

• Standard 20mm ball sockets for broad cross-brand compatibility
• Not suitable for 25.4mm / 1" / B-sized systems
• Works with Tackform 20 Series bases, clamps, and device holders
• Engineered load capacities and tested durability for reliable performance

How does the optional anti-theft knob work and when should I use it?

The optional patent-pending anti-theft knob adds a simple mechanical resistance to the socket interface to deter quick snatch-and-grab removal. It’s helpful for exposed installations — motorcycles, UTVs, or public-facing vehicles — where extra retention is desirable without changing mount geometry.

• Anti-theft knob increases resistance between ball and socket
• Prevents accidental or casual removal if not fully tightened
• Can be used selectively when mounting in unsecured or public environments
• Remains optional — arm works normally without the knob installed

What makes the DuraLock 20 Series different from cheaper 20mm parts?

Tackform emphasizes tested durability and a conservative safety factor, with metal construction and precision machining aimed at long-term reliability. The DuraLock series focuses on repeatable clamping performance and predictable load handling, rather than minimal-cost materials that can loosen or deform under stress.

• Metal construction for stiffness and longevity
• Precision 20mm ball-and-socket tolerances for consistent clamping
• Tested load capacities and engineered safety margins
• Matte black finish for corrosion resistance and low-glare aesthetics

Who is this for: The Tackform DuraLock 3.5" dual 20mm arm is ideal for riders, off-roaders, and professionals who need a compact yet highly adjustable mount that won’t compromise strength. Choose this arm if you already use the 20mm ecosystem and want a robust metal link that offers wide articulation, proven load-handling, and the option of an anti-theft knob for extra retention in exposed situations. If you require compatibility with 1"/25.4mm ball systems, select a B-sized product instead.