Holosun has officially retired its long-standing 403 and 503 series rifle red dots. In their place, they’ve launched the ARO and ARO-EVO lines—new optics designed to bring updated features, better construction, and more versatility to the budget-friendly red dot market.
We’re breaking down the differences between the original 403 series and its modern replacement, the ARO series, so you can decide whether it’s time for an upgrade or just get up to speed on the changes.
A Quick Look Back: The 403 Series
The 403 series was Holosun’s go-to budget rifle red dot for years. It came in three versions—each with varying features:
- 403R: The most barebones of the bunch. It had a rotary dial for brightness adjustment, no shake awake, and no solar panel. Built with a cast aluminum housing, it was available with a red or gold reticle.
- 403B: A step up, featuring button controls and Shake Awake. It used a stronger 6061 aluminum housing, and came in red or green reticles. Holosun also released an FDE housing version of the 403B.
- 403C: The premium option in the lineup. It included both Shake Awake and a solar panel, giving it an auto brightness mode. It was also compatible with Holosun’s HM3X magnifier.
All 403 variants featured:
- 2 MOA dot only
- 20mm objective lens
- Included mounts: 1.63” lower 1/3 co-witness and 0.75” low mount
Meet the Future: The ARO Series
The ARO series is Holosun’s modern answer to the 403 lineup. It’s built to be the next-generation budget red dot—bringing updated features, more reticle options, and improved construction.
Here’s what the ARO series offers:
- 6 versions total, including:MRS (Multi-Reticle System): 65 MOA circle + 2 MOA dot, toggleable or MOA dot only version
- Reticles available in Red, Green, and Gold
- 22mm objective lens (slightly larger than 403’s 20mm)
- Window size: 22mm (0.86")
- Aluminum body
- Shake Awake included on all models
- Mounts included: New 1.63” lower 1/3 co-witness pedestal mount and a low mount measuring 1.055”
The new mounts remind me of the SCRS series, but the ARO is a T1/T2 footprint, just like the 403 series.
What’s the Same, What’s Improved?
|
Feature |
403 Series |
ARO Series |
|
Reticle |
2 MOA dot only |
2 MOA dot or MRS (65 MOA + 2 MOA) |
|
Reticle Colors |
Red, Green, Gold (varies) |
Red, Green, Gold |
|
Shake Awake |
Only on 403B & 403C |
Standard on all models |
|
Solar Panel |
403C only |
Not included |
|
Window Size |
20mm |
22mm |
|
Body Material |
Cast or 6061 Aluminum |
Aluminum (modernized design) |
|
Mount Height Options |
0.75” low, 1.63” co-witness |
1.055” low, 1.63” pedestal mount |
|
Weight |
2.82 oz |
3.38 oz |
Final Thoughts
The ARO series keeps the budget-friendly spirit of the 403 line alive but brings it up to modern standards. With Shake Awake as standard, a larger window that pairs perfectly with the Holosun HM3X magnifier, more reticle options, and a cleaner mounting system, it’s a clear upgrade for new buyers or anyone looking to refresh their setup.
While you won’t find a solar panel like you did on the 403, it is on the higher end line the ARO-EVO. And with MRS versions available, the ARO series offers flexibility that the 403 never had.
Whether you’re building a new rifle or upgrading an old one, the ARO is a worthy successor to the discontinued 403—and a solid pick for any budget-conscious person.
