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Sig Sauer
Overview
The Sig Sauer Romeo4S is a 1x20 red dot optic designed for quick target acquisition, featuring a 2 MOA dot size that provides precise aiming without obstructing your view. The optic is finished in a gray color and utilizes a red reticle for enhanced visibility in various lighting conditions, making it suitable for both tactical and recreational shooting. This optic is commonly found on carbine builds chambered in 5.56 NATO, where speed and accuracy are paramount.
Specifications
SIG Sauer Romeo4S 1x20 2 MOA Solar Red Dot Optic - SOR43021
Build history on GunPartPicker
Builders have added the SIG Sauer Romeo4S 1x20 2 MOA Solar Red Dot Optic - SOR43021 to their builds on GunPartPicker. Since April 2026, it ranks #101 of the 586 optics builders have added. Builds with this optic are nearly all chambered in 5.56 NATO, mostly on carbine-length gas (67%, then mid-length 33%), and nearly all AR-15.
It was hard to find in October 2026, in stock on only 7 of the 16 days we checked, and today none of the 3 retailers we track has it in stock right now. Prices barely moved in October 2026, holding around $439.99, with no real sale all month. Listed prices start at $316.64 at BattleHawk Armory for when it comes back.
Updated · from real builds on GunPartPicker · Prices checked · refreshed daily across 37 retailers
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Read the guide: AR-15 Red Dot & Optic Guide →Check it against the live catalog:
Frequently Built With
The part most often added in each category by the builds that include this one
Geissele Automatics AR-15 SSA X Lightning Bow Trigger
Bravo Company Mfg Upper Receiver Assembly w/ Laser T-Markings, Hard Coated Anodized - 4-UR-M4
Aero Precision Stripped M4E1 AR-15 Lower Receiver - Special Edition - Freedom
Magpul MOE MVG Vertical Grip - Flat Dark Earth
Strike Industries Ambidextrous Magazine Release, Black - ARAMBIMRBK
Strike Industries Extended Bolt Catch
Build Configuration Breakdown
Aggregated and anonymized data showing how builders use this product
Gas SystemBased on real build data showing which gas system lengths builders use with this product.
Builds Featuring This Part
See all builds →Builds in the community that include the Sig Sauer Romeo4S 1x20 2 MOA Solar Red Dot Optic - SOR43021
| Build | Parts | Total |
|---|---|---|
 | 32 | $3883.80 |
 | 32 | $3883.80 |
 | 13 | $1563.03 |
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