Description
Transform your Holosun 510C red dot sight from absolute to lower 1/3 co-witness with this precision-engineered aluminum spacer.
Achieve optimal sight alignment and a more comfortable shooting position with your Holosun 510C. This spacer raises your optic height to 1.63 inches, positioning iron sights in the lower third of your field of view rather than blocking the center. The result is a cleaner sight picture with your red dot while maintaining quick access to backup iron sights if needed. By elevating the optic just 0.22 inches, this spacer helps many shooters achieve a more natural cheek weld without craning their neck, particularly beneficial during extended shooting sessions or when wearing hearing protection.
Key Features
- Precision Machined 6061 T6 Aluminum: Aircraft-grade aluminum construction provides durability and corrosion resistance while adding only 1 ounce to your setup
- Lower 1/3 Co-Witness Height: Raises optic centerline to 1.63 inches, placing iron sights in the lower third of your viewing window for an unobstructed red dot sight picture
- Anodized Finish: Hard anodized surface treatment matches the 510C finish and provides enhanced wear and corrosion resistance
Important Compatibility Notes
- Designed specifically for Holosun HS510C and HE510C models (both red and green dot versions)
Why We Carry It
The Holosun 510C ships from the factory with an absolute co-witness mount, placing the optic at 1.41 inches. While this works for some shooters, many find themselves looking through the top portion of the sight window with a standard AR-15 cheek weld. The absolute co-witness configuration places iron sights directly in the center of your viewing window, which can create a cluttered sight picture. This spacer became one of the most requested Holosun accessories after competitive PCC (pistol caliber carbine) shooters discovered that raising the optic improved both comfort and target acquisition speed. The lower 1/3 configuration keeps your backup irons visible and zeroed but moves them to the bottom of your field of view, giving you a wider, cleaner window for the red dot itself.
Frequently Asked Questions
What’s the difference between absolute and lower 1/3 co-witness?
Absolute co-witness places your iron sights and red dot at the same height, with the iron sights visible in the center of your optic window. Lower 1/3 co-witness raises the optic slightly so iron sights appear only in the bottom third of the window, providing a less obstructed view of your red dot while still allowing you to use backup irons by adjusting your cheek weld slightly lower.
Do I need to re-zero my optic after installing this spacer?
Yes, any change in mounting height will affect your zero. You’ll need to re-zero your 510C after installing the spacer. However, if you’ve already zeroed your backup iron sights, they will maintain their zero, and you can use them as a reference point when zeroing the raised optic.
Will this spacer work with the Holosun HM3X or other magnifiers?
Yes, this spacer pairs well with magnifiers. Many users specifically add this spacer when using the HM3X 3x magnifier to achieve proper eye alignment and a better cheek weld, especially when wearing over-ear hearing protection. The raised height helps align the optic with magnifiers mounted at lower 1/3 height.
Spec Sheet
- Material: 6061 T6 Aluminum
- Surface Finish: Anodized
- Height Addition: +0.22 inches (raises optic from 1.41″ to 1.63″)
- Final Optic Height: 1.63 inches (Lower 1/3 Co-Witness)
- Dimensions: 1.6″ (L) x 0.98″ (W) x 0.95″ (H)
- Weight: 1 oz
- Compatibility: Holosun HS510C, HE510C (all variants)
- Color: Black
- Manufacturer Part Number: 510CSPACER
