Archery · Archery Arrows · Archery Arrows 101 · Archery Guide · arrow shaft ·Oct 22, 2025

The Ultimate Guide to 4mm Arrows: Why Micro-Diameter Shafts Deliver Superior Penetration and Accuracy

by Zakk Plocica

What Are 4mm Arrows?

When it comes to maximizing penetration, accuracy, and consistency, 4mm micro-diameter arrows—also known as micro-diameter arrows or .166 shafts—are becoming one of the most popular choices among serious bowhunters.

These arrows feature a smaller shaft diameter compared to traditional 5mm or 6.5mm shafts, giving them a slimmer profile and superior flight characteristics. Whether you’re shooting 3D targets or hunting in open country, .166 arrows offer real-world performance advantages that can make or break your shot.

Key Benefits of 4mm Arrows

1. Deeper Penetration and Pass-Throughs

The smaller surface area of .166 arrows means less drag and resistance when hitting flesh or bone—similar to how a thinner knife blade slices more efficiently.

Less drag = more kinetic energy through the target.

That translates into:

Deeper wound channels
More reliable pass-throughs
Better blood trails
Higher recovery rates on big game

This makes micro-diameter arrows a top choice for hunters chasing elk, moose, and other large game where every inch of penetration counts.

2. Improved Wind Resistance and Accuracy

One of the most overlooked advantages of 4mm arrow shafts is their ability to fight the wind. With less surface area, there’s less arrow to be pushed off course by crosswinds—critical for long-range shots.

In windy western conditions or when shooting 60+ yards, a 4mm micro shaft maintains stability and stays closer to center, ensuring you hit where you aim.

Perfect for:

Western bowhunts in open plains
Total Archery Challenge-style 3D courses
Long-range practice sessions

3. Better Energy Retention and Flatter Trajectory

The aerodynamics of micro-diameter arrows work in your favor. A recent Easton ballistic study revealed that 4mm shafts experience less drag than 5mm arrows which experience up to 10% less drag than a standard diameter arrow shaft.

That means they:

Maintain speed longer over distance
Deliver more kinetic energy on impact
Provide a flatter trajectory for easier distance estimation

This gives bowhunters added confidence when taking those unpredictable, real-world shots where animals rarely stand perfectly still or at a known distance.

Trade-Offs to Consider

While 4mm micro-diameter arrows deliver serious performance, there are some considerations to keep in mind before making the switch.

Higher Component Costs

Because of the smaller diameter,.166 arrows require specialized components like Deep Six inserts or outsert systems—which are generally more expensive and limited in availability. Premium systems like titanium or stainless steel outserts offer the best strength but increase cost and total arrow weight.

Precision Build Required

Micro shafts demand tighter tolerances. A misaligned or poorly glued outsert can cause broadhead flight issues. That’s why at Extreme Outfitters, we offer free arrow cut, square, and glue service—ensuring every arrow you receive is built to perfection.

Durability Considerations

Aluminum outserts (like those found on some stock setups) can bend if they hit hard surfaces. We recommend upgrading to titanium outserts for maximum strength—especially if you’re a serious hunter pushing heavy setups.

Easton Axis 4mm

55-grain half-out aluminum system
Match Grade construction with O-ring alignment
Exceptional straightness and consistency

Victory VAP TKO

50-grain Shock Outsert for improved penetration
Advanced carbon construction for tight tolerances
Lightweight yet deadly accurate at long range

Both are available individually—so you can buy just a few to test—or by the dozen for your next hunt.

Shop Easton Axis 4mm and Victory VAP TKO arrows here at Extreme Outfitters

and take advantage of:

Free cut and glue service
Free shipping on orders over $50
Expert tuning advice from real bowhunters

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Victory VAP TKO Elite Hunting Arrow Shaft

USD 20.41