Monstrum 1-4x20 Rifle Scope with Rangefinder Reticle - Compact Low

Our review of the Monstrum 1-4x20 finds it best suited for shooters who want a compact, low power variable optic for close to mid-range work; the single biggest reason to consider it is the combination of clear glass and a built-in rangefinder reticle that speeds up range estimation and holdover correction in fast-moving scenarios. The scope's modest size and 1-4x magnification make it a practical choice for patrol rifles, home defense builds, or hunting in thick cover, and this review focuses on real-world handling, optical clarity, and the scope's usability under typical field conditions.

Key Features

• 1-4x Magnification: Provides a wide field of view at 1x with the ability to zoom to 4x for more precise shots at mid range.
• Rangefinder Reticle: Built-in marks give faster range estimation and simpler holdover correction without needing a separate tool.
• Nitrogen Filled Tube: Internal nitrogen filling resists fog and moisture for reliable performance in changing weather.
• Compact Size and Weight: At roughly 8.5 in long and 11 oz, it balances low bulk with durability for lightweight rifle setups.
• 1/2 MOA Adjustments: Windage and elevation click at 1/2 MOA for fine tuning and repeatable zeroing.
• Included Accessories: Ships with lens covers and a 3V CR1632 battery so the illuminated reticle is ready out of the box.

Who It's For

The Monstrum 1-4x20 is aimed at shooters looking for a practical low power variable optic for close to mid-range engagements, including hunters who work in woodland and brush, tactical shooters on patrol rifles, and any user who values a fast 1x feel with some magnification for follow-up shots. The fixed compact footprint and rangefinder reticle make it especially useful for scenarios where speed and quick range estimation matter.

Shooters who need very long-range precision, advanced ballistic turrets, or a front focal plane reticle for holdovers that scale with magnification should look elsewhere; this is a second focal plane scope focused on short to mid-range flexibility rather than extended-range dialing.

Pros & Cons

Pros

• Clear optics across the 1-4x range make target acquisition quick at 1x and usable at 4x.
• Rangefinder reticle speeds ranging and holdover without extra devices.
• Durable, nitrogen filled tube helps prevent fogging and handles outdoor conditions.
• Compact, lightweight profile keeps the rifle balanced and maneuverable.

Cons

• The second focal plane reticle does not scale with magnification, which limits ranging precision at higher zoom.
• Does not include high-end turret features for long-range ballistic compensation.

Specifications

Our Verdict

The Monstrum 1-4x20 is a solid value for anyone needing a compact LPVO that emphasizes rapid target acquisition and simple ranging with a built-in reticle. It is especially good for close to mid-range hunting and tactical use where weight and speed matter, offering reliable optics, fog resistance, and usable adjustments at a competitive price point.

Frequently Asked Questions

Is the reticle illuminated?
The scope includes a battery (3V CR1632) for reticle illumination when needed.

Is this scope waterproof or fog proof?
Yes, the tube is nitrogen filled to resist water and fog under normal field conditions.

Does the reticle scale with magnification?
No, the reticle is in the second focal plane and does not change size with magnification.