ERA-TAC Angle Cosine Indicator (ACI) Mil-Spec.

• Angle cosine compensation: The ACI helps account for the trajectory change that occurs on steep uphill or downhill shots, making hold or correction decisions more reliable in long-range shooting.
• Integrated bubble level: The built-in level helps prevent rifle cant, which reduces lateral point-of-impact shift and supports more consistent precision at distance.
• Mil-Spec waterproof design: This version is built to remain waterproof for 35 minutes at 1 meter depth, adding confidence for field use in rain, wet terrain, and harsh weather.
• UNIVERSAL-Interface compatibility: It mounts to the ERATAC interface without changing riflescope position, so the rifle can be upgraded with angle and level control while preserving the existing optic setup.
• Compact aluminum construction: The light 30.00 g weight and aluminum body add useful shooting information with minimal effect on overall rifle balance.

About the ERA-TAC Accesories Series

The ERA-TAC Accesories series forms the support side of the ERATAC tactical mounting system, giving shooters practical add-ons that expand a rifle setup without unnecessary bulk. Introduced under the ERATAC brand for the civilian market and law enforcement, this accessory family is built around modularity, especially where the UNIVERSAL-Interface allows different tools and adapters to be added in a compact, secure way.

Within the series, the focus is on field-relevant functions rather than cosmetic extras. Adapters, Picatinny interface parts, spacers, sling-related components, and angle cosine indicators are designed to solve specific mounting and shooting problems while keeping the rifle streamlined. A key characteristic of the line is that accessories are meant to integrate cleanly with tactical optics and related equipment, including lasers, flashlights, and support tools. The angle cosine indicator with bubble level is a good example of that design approach: it adds information that matters for steep-angle shooting while also helping the shooter keep the firearm level. Across the range, ERATAC accessories are intended for hunting optics, tactical optics, and precision shooting setups where repeatable mounting and efficient use of space are important.

About the ERA-TAC Angle Cosine Indicator (ACI) Mil-Spec.

The ERA-TAC Angle Cosine Indicator (ACI) Mil-Spec. is a compact shooting aid made for riflescope setups where steep-angle shots and rifle cant can both affect accuracy. Its main role is to help the shooter compensate for the gravity-related trajectory difference that appears when firing sharply uphill or downhill. In practical terms, that makes it especially relevant for long-range and precision shooting in mountainous terrain, elevated hides, training environments, or tactical positions where the line of fire is not flat.

The integrated bubble level adds a second layer of correction by helping the shooter keep the rifle level before breaking the shot. That matters because cant can introduce point-of-impact shift, particularly as distance increases. ERATAC positions the indicator so it can be read while the rifle is already mounted, and the lateral placement of the level helps keep the elevation turret visible. This supports faster checks without disrupting the shooting position.

Because it is designed for the ERATAC UNIVERSAL-Interface, the ACI can be added without repositioning the riflescope, which is an important advantage on tightly configured rifles. The Mil-Spec. version also adds waterproof construction for 35 minutes at 1 meter depth, making it better suited to hard outdoor use. With its aluminum body and low 30.00 g weight, it adds useful shot-angle and leveling information without noticeably increasing rifle bulk.

About ERA-TAC

ERA-TAC is a brand of Recknagel GmbH & Co. KG, based in Bergrheinfeld, Germany. Recknagel was founded in 1867 in Albrechts near Suhl, Thuringia, and has long specialized in firearm-related components and accessories. Its product portfolio covers solutions for hunting, sport, and tactical firearms, which gives the company a broad foundation in both traditional and modern mounting systems.

The ERATAC line was introduced in 2010 to focus on tactical mounts and accessories for civilian and military markets. The brand is known for robust mechanical design, with mounts machined from solid aluminum and finished with Mil-Spec Type III hard anodizing. The range includes tactical riflescope mounts, Picatinny rails, backup sights, and weapon accessories, reflecting a strong emphasis on repeatable mounting, durability, and practical field use.

Main Features

• Manufacturer: ERA-TAC
• Series: ERA-TAC Accesories
• Made in: Germany
• Accessory type: Angle cosine indicator
• Accessory for: Riflescopes
• Material: Aluminium
• Weight: 30.00 g
• Color: Black

Warranty

ERA-TAC provides a 2-year warranty for this accessory. That period suits a precision-machined mounting component intended for regular field and range use.