Buy Now, Pay Later
As low as
$15.83
/ mo
Learn more
- – 6-month term
- – No impact on credit
- – Instant approval decision
- – Secure and straightforward checkout
Ready to go? Add this product to your cart and select a plan during checkout.
Payment plans are offered through our trusted finance partners Klarna, PayTomorrow, Affirm, Afterpay, Apple Pay, and PayPal. No-credit-needed leasing options through Acima may also be available at checkout.
Learn more about financing & leasing here.
Selected Option
Free shipping on this product
30-day returns
Learn more
30-day refund/replacement
To qualify for a full refund, items must be returned in their original, unused condition. If an item is returned in a used, damaged, or materially different state, you may be granted a partial refund.
To initiate a return, please visit our Returns Center.
View our full returns policy here.
Availability:
In Stock.
Arrives
Oct 2 – Oct 3
Recently Viewed
Style: Guardian | 4-12x50 AO
Features
- Adjustable 4-12 times magnification, for targeting out to 800 yards and beyond
- An adjustable objective lens or AO - that allows for sharper focus of the target image, elimination of parallax, and range estimation
- Aircraft grade 6061 aluminum scope body with a sealed, nitrogen-charged tube for resistance to water and fog
- Precision 1/4 MOA/click windage and elevation adjustments with locking turrets
- Package includes High Profile Picatinny/Weaver Scope Rings and set of flip-up lens covers
Brand: Monstrum
Color: Black
Style: Guardian | 4-12x50 AO
Sport: Hunting
Item Weight: 15 Ounces
Material: Aluminum
Magnification Maximum: 12 x
Objective Lens Diameter: 50 Millimeters
Magnification Minimum: 4 x
Compatible Devices: Rifle
Brand: Monstrum
Color: Black
Style: Guardian | 4-12x50 AO
Sport: Hunting
Item Weight: 15 Ounces
Material: Aluminum
Magnification Maximum: 12 x
Objective Lens Diameter: 50 Millimeters
Magnification Minimum: 4 x
Compatible Devices: Rifle
Mounting Type: Picatinny Mount
Night vision: No
Eye Relief: 3 Inches
Model Name: Guardian 4-12x AO
Manufacturer: Monstrum
Reticle Type: Crosshair Reticle
UPC: 810088812026
Item Package Dimensions L x W x H: 15.98 x 3.39 x 3.03 inches
Package Weight: 0.94 Kilograms
Brand Name: Monstrum
Part Number: SG41250AO-B
Included Components: Guardian Scope, One Pair High Profile Scope Rings, One Pair Spring-Loaded Flip-up Lens Covers
Date First Available: August 23, 2022
Frequently asked questions
If you place your order now, the estimated arrival date for this product is:
Oct 2 – Oct 3
Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.
To initiate a return, please visit our Returns Center.
View our full returns policy here.
To initiate a return, please visit our Returns Center.
View our full returns policy here.
- Klarna Financing
- Affirm Pay in 4
- Affirm Financing
- Afterpay Financing
- PayTomorrow Financing
- Financing through Apple Pay
Learn more about financing & leasing here.
Similar Products
Top Amazon Reviews
Style: Guardian | 3-9x40 AO
I don’t think it is possible to get a better scope for the money. When my scope was delivered, I was amazed at the quality and features it had. Unfortunately, there was a defect in the scope where something was obstructing the view inside the opticals. I set up a return with Amazon and had a new scope delivered in 3 business days. I could have returned this scope and then bought a different one but I liked the look, the feel, the optics, the lighted reticles and the price. I also really like the lens covers as well. Mounting the scope was easy and the mounting hardware is excellent quality. This scope is perfect for my little .22 rifle and is easy to set up and sight in. The objective control and magnification controls are not the smoothest I have ever used, but the optics on this scope are quite simply amazing for the price. You really cannot go wrong with this scope!
...
show more
Reviewed in the United States on June 6, 2023 by Melissa Follett Melissa Follett
Style: Guardian | 4-12x50 AO
Pretty clear glass and great zoom. Hold zero petty well very nice quality for the price good for dmr or bolt action applications pretty good eye relief would buy again
Reviewed in the United States on June 3, 2025 by RiddleRifleCompany
I've taken this to the range a couple of times, fired 100+ rounds and it has held up well. When zeroed it has done well. The problem is the rings won't hold it still. My last attempt with thread locker and good torque wouldn't keep it from sliding and scratching up the bottom of the scope body. I am only shooting a medium powered cartridge so it shouldn't fail. I'll buy some better rings for it. I advise you to as well if you pick up this scope.
...
show more
Reviewed in the United States on September 2, 2024 by MWAnderson
Style: Guardian | 4-12x50 AO
Great scope for my 22 lr. Other than that it wouldn't use it on my larger caliber rifles.. but it would fit perfectly on any of my rifles.
Reviewed in the United States on June 19, 2025 by NATE
Style: Guardian | 6-18x50 AO
My Monstrum Guardian Series AO Rifle Scope with Parallax Adjustment, is a Second Focal Plane scope (my preferred Focal Plane for long-range shooting [750yds+]). The glass is perfect (clear, sharp presentation of illuminated crosshairs, and no halo or fog), and the 1" tube is solid and well made. The 1/4 MOA/click windage and elevation adjustable turrets have screw-on covers to keep your adjustments secure once zeroed, and the clicks are smooth and positive. I have a couple of scopes costing 10 times more than the Monstrum Guardian Series AO Rifle Scope, and I bought it "just to check it out" because of the low-end price. I have used several Monstrum cantilever mounts, and other Monstrum products which impressed me enough to try their optics, and the Monstrum Guardian Series AO Rifle Scope with Parallax Adjustment surpassed my expectations. Monstrum provides an outstanding scope at a bargain price in the 6-18 power range. You are reading this review, and I have NO association with Monstrum other than as a customer, so if you're looking for a 6-18 variable optic, I STRONGLY recommend the Monstrum Guardian Series AO Rifle Scope! If you don't like it and bought it from Amazon, you can return it for credit or replacement.
...
show more
Reviewed in the United States on December 5, 2023 by Gil
Style: Guardian | 4-12x50 AO
I bought this to replace the Viridian junk that came mounted on my 10/22. It's simply awesome. Great eye box, wonderful eye relief, and that big 50mm objective lets in a ton of light; so much so I haven't even needed the illumination at the range. I will say that there is a lot of light bleed at the higher settings of illumination, but as none is typically necessary, it's not a big deal at all. The throw lever is a bit stiff, but is starting to smooth out under use. The picture is clear at all magnifications, and the adjustable objective is a game changer. I've never used an AO scope before, MD this is just fantastic. Unlike the POS it replaced, I see a clear target instead of fuzzy mush. While I don't know if it'll hold up to larger calibers, for .22 it's fantastic. The price point is almost ridiculous for a scope like this. I would 200% buy it again.
...
show more
Reviewed in the United States on January 8, 2023 by Amazonian Customerers
Style: Guardian | 4-12x50 AO
This scope came highly recommended from piers, I am not sure if I had a faulty scope or not, however I went through 2 boxes of ammo after getting it professionally mounted and bore sighted. So here is the story.. Went to local gunsmith got 30-06 with Guardian mounted and bore sighted and I asked for him to come with me to the gun range so we took off to shoot. Set target up at 100 yards and got it adjusted only after 3 shots then fired 4 more, perfect bullseye 3 out of 4 shots. Move target to 200 yards first shot low right by 4" to the right and 5" low (weird) shoot again and this time 3 out of 4 shots never hit the paper. I let the gunsmith try and same results. We tried a few more shots then back to 100 yards and we were all over the paper at 100 yards. No consistency. Back to the gunsmith shop, bore sighted and back to the range once again pretty much the same thing! 300 yards and not even a fracture of a bullet hitting the paper. This was done in a vise with two different people.
...
show more
Reviewed in the United States on December 26, 2023 by Amazon Customer
Style: Guardian | 6-18x50 AO
The scope came bagged up in an unsealed box with the illumination battery installed. No factory tape or indications on the carton , bag, or scope suggesting this was a new item, if it was inspected for quality at the factory or if this was a return put back into stock. It does work. At 50 and 100 yards with a pistol caliber AR platform rifle I was able to see my hits on a reactive (shoot n see) target. The eye relief is all or nothing. A very narrow window between decent clarity and a blurred mess. For what I want in an inexpensive scope for range plinking it works. No complaints. This is a rather large scope and on a pistol caliber AR platform rifle it may seem big for the rifle.
...
show more
Reviewed in the United States on December 9, 2024 by Home Brew Audio