Osuma Single Ring for Osuma Base, 40 mm

• 40 mm scope fit: Built for scopes with a 40 mm main tube, this ring gives the large-contact support needed to hold heavier optics securely and help maintain alignment under recoil.
• Single upper ring for modular mounting: As a dedicated top ring for the Osuma Base system, it lets shooters replace a worn or damaged upper half without changing the whole mount assembly.
• Compatible Ø 7 mm interface: The ring works with Osuma, Optilock, EAW and Recknagel Ø 7 mm interfaces, making it useful when matching existing bases across several common mounting systems.
• Aluminium construction: The aluminium body keeps weight down while still providing the rigidity needed for a stable scope hold on hunting and sporting rifles.
• Made in Finland: Finnish manufacture reflects Osuma’s focus on practical rifle-mounting hardware designed around real hunting and shooting use rather than generic accessory dimensions.

About the Osuma Osuma Base Rings Series

Osuma Osuma Base Rings are part of the brand’s fixed scope-mount system, built around a simple and serviceable three-part layout of base, bottom ring and top ring. That design makes the series especially practical for shooters who want a mount that can be configured around the rifle, the rail type and the scope tube diameter without replacing the entire setup. Within the series, Osuma offers ring sizes for 1 inch, 30 mm, 34 mm, 36 mm and 40 mm scope tubes, with height options varying by tube size.

The series sits squarely in Osuma’s hunting and sporting optics range, where the emphasis is on secure mechanical fit, straightforward installation and compatibility with several common base types. Osuma positions these rings for use with its own bases on 11 mm, 17 mm, Sako, Picatinny and Tikka M55/M65 platforms, giving the system broad relevance across European rifle setups. The rings are made from high-grade aluminium with an anodized surface, combining low weight with the corrosion resistance and surface durability expected from field-use mounting hardware.

About the Osuma Single Ring for Osuma Base, 40 mm

The Osuma Single Ring for Osuma Base, 40 mm is a replacement or build-component upper ring made for shooters using a 40 mm scope tube in the Osuma Base system. In practical terms, this part is aimed at maintaining or completing a fixed mounting setup for larger-tube optics, where precise ring fit matters for even clamping pressure and stable scope positioning. A 40 mm tube is usually found on more specialized optics, so the ring’s job is not just to hold the scope, but to do so without introducing unnecessary stress into a larger and often heavier sight.

Its aluminium construction keeps the assembly lighter than a comparable steel part, which helps when balancing a rifle already carrying a substantial optic. The black finish gives the ring a subdued appearance that matches most modern riflescope bodies and mounting components. With KR 0.0 mm extension, this version is a straightforward non-offset ring, intended for setups where the scope’s eye relief and mounting position are already correctly established by the base and lower ring arrangement.

A key advantage of this model is its compatibility with the Ø 7 mm interface used by Osuma, Optilock, EAW and Recknagel bases. That makes it useful not only as an Osuma spare part, but also as a practical solution for shooters working within established European mounting standards. For hunting optics and general rifle scope mounting, it offers a clean way to restore, adapt or complete a fixed mount without changing the rest of the system.

About Osuma

Osuma is a Finland-based manufacturer focused primarily on rifle scope mounting. The company’s background goes back to the early 1990s, when its owner began developing mounts for his own hunting and benchrest shooting needs. That origin still shows in the product range, which is centered on practical mounting solutions rather than broad general accessories.

Today, Osuma’s catalog includes scope mounts, scope rings, rail mounts, red-dot and holosight mounts, and suppressors, with products designed and manufactured in Finland. The brand is particularly known for offering mounting solutions across several rifle and rail standards, including 11 mm, Tikka 17 mm, Sako, Picatinny, Optilock and Blaser systems. Its scope rings are made from aluminum with an anodized surface, reflecting the company’s emphasis on durable, field-ready mounting hardware. Osuma remains a family business that has passed from father to son.

Main Features

• Manufacturer: Osuma
• Series: Osuma Osuma Base Rings
• Made in: Finland
• Material: Aluminium
• Extension (KR): KR 0.0 mm
• Scope / sight fit: 40 mm
• Color: Black
• Compatibility above: 40 mm
• Compatibility below: EAW Ø 7 mm Interface, Optilock Ø 7 mm Interface, Osuma Ø 7 mm Interface, Recknagel Ø 7 mm Interface

Warranty

Osuma provides a 2-year warranty for this mount component. That period matches the warranty stated for the product and suits a precision-machined mounting part intended for regular field and range use.