The Altra Insert and Outsert.166 250 Spine is a modular arrow component designed for archers who want precise spine matching and easy field tuning. This 12-pack provides a 250-spine option within the Insert and Outsert system, plus the ability to fine-tune with micro FMS insert weights.

• Pack Size: 12-pack quantity for convenient replacements and on-the-fly tuning in the field
• Spine Options: Available in 250, 300, 350, and 400 spine variants to match your bow’s draw weight and arrow setup
• Total Weight: 50 grains total weight to help balance and stabilize arrow flight
• Compatibility: Accepts micro FMS insert weights for precise weight adjustments without swapping major components
• System Type: Designed for the Altra Insert and Outsert ecosystem, enabling quick, modular changes
• Interface: Aligns with the.166 insert/outsert specification for reliable performance and consistency

This insert/outsert combo is ideal for serious archers who tune every variable—from spine to total arrow weight—to achieve consistent flight and tight groupings. Use the 12-pack to experiment with different spine profiles and micro-weight configurations, ensuring your arrows perform best across varying bows, strings, and conditions. The modular design minimizes downtime and helps you quickly adapt to new setups, practice scenarios, or seasonal changes in draw weight.