Product FAQs

What is the Derry warranty?

Answer: Derry offers 5 years warranty for our products. For any problems, if you can not solve it . Please contact us firstly, After our evaluation, send back the product to us. After we repair it, we will send it to you again.

How long does it take to process an order?

Answer: Most in-stock orders ship within 1-2 days from our warehouse. Orders that are for custom-built products, may take slightly longer to fulfill. For faster delivery, please tell us an expedited method of shipment at the time of ordering. On the rare occasion an item is not available for immediate shipping, you will be notified with an estimated time of arrival for the item. Once contacted, you may allow the order to continue or make any adjustments, including cancellation, if desired. If an order cannot ship in its entirety, Derry reserves the right to hold the order until all items are in stock or to send as items become available.

How to Purchase Our Products?


If you want to buy items in retail please go to our online store


If you are retail dealers or want to be distributors please e-mail ( to us to acquire our standard quotation list. We will be much appreciated that we can have some initial information of your company and market.

Why am I seeing glare?

Answer: Some amount of glare may be present in reflective/reflex optical sights at specific/odd angles due to the special reflective coatings on the objective lens.

Glare is more apparent in low light and indoors when there is overhead or back-lighting. Glare will be exaggerated when the optic is held in the hand instead of mounted because you can pan the optic to angles that you will not experience during use .

Why don’t I see a perfect round dot? Instead I see a splashed dot, half-moon shape, multi dot, starburst etc?

Answer: It is very likely (99% chance) you have astigmatism that you are not aware. What you see is a small reflex of led light bulb on the lens. One simple and quick way to find out is to use your cellphone to take a photo of the dot at medium brightness setting. If you see a circle dot in the photo you took, you basically diagnosed you have Astigmatism(Because cellphone is a machine does not has astigmatism). Many users decide to continue to use the imperfect dot, or use a bigger MOA red dot such as 6MOA instead 3MOA. Some users also see green dot better than red dot, it really depends on the individual case. Or user can use a totally different optics which is not an reflex sight such as an rifle scope instead. 

Why this sight does not fit my handgun plate/cut?

Answer: Derry model DE1309, DE1316 are designed to fit the mounting plate made for Vortex venom, burris fastfire, meopta, eotech mrds, docter, insight that REPLACE the rear sight. It does not fit trijicon rmr and shield rms footprint. 

DE1309, DE1316 all fit directly on the Pre-cut on the slide on “Optics Ready Pistols” that keeps the rear sight like Glock MOS, Smith Wesson MP C.O.R.E  and Springfield XD OSP.  Those "Optics Ready" handguns all come with several mounting plates marked for different brands of red dots, such as for Trijicon RMR, Shield RMS and Vortex. Our red dots use the pistol manufacturer provided plate marked for Doctor/Vortex Venom type red dot. 

What is the torque to install screws?

Answer: Torque screws to 12 IN/LBS. Please do not over tighten the screws. Using gun glues.

I pressed the power button, but it is not powering on.

Answer: There are many brightness settings. Press and hold the switch for 3 seconds to turn on or off. Quick press will NOT turn on or off the red dot. For models with Up Arrow and Down Arrow, Hold Up Arrow for 3 secs to power on, and hold Down Arrow for 3 secs to power off.

To adjust brightness, quick press to adjust the brightness from low to high. When you first turn it on, it will be at the lowest setting. This setting is invisible to human eyes, it can only be seen through a night vision device. We received quite a few returns because user can't see it and think it is defective. Please press the switch to cycle through the brightness until you see a bright dot. 

I tried to use the allen wrench provided to adjust the elevation and windage screws, dot is not moving.

Answer: There are two LOCKS screws at the rear end. Please loosen the LOCK screws before adjusting the elevation and windage. After adjustments then tighten the LOCK screws again. Without loosening the LOCK screws the elevation and windage screws cannot work and will permanently damage it. 

I turned the elevation screw all the way to the end where it can’t turn anymore, but my dot is still too high.

Answer: Some firearms require a red dot shim/riser to rise the red dot a bit. It happens with many red dots. Please go online to search ‘Red Dot Sight Shim’ to purchase one for your red dot. We recommend getting the shim from Derry or “UM Tactical” who is offering the shim for many name brands.

I cannot attach my red dot to my xxx handgun.

Answer: When you first receive the red dot. It has a picatinny mounting plate pre-assembled. Please use the allen wrench provided to take out the 2 hex screws on the top behind the glass frame. It will disconnect the red dot from the picatinny mounting plate. You will then be able to attach the red dot to a variety of handgun mounting plates that are sold separately. There are many popular handguns on the market, due to the size difference of the handguns, each mounting plate is slightly different in dimensions. There are also many manufacturers making a variety of handgun plates that replace the rear sight, including ADE, Lakeline LLC, EGW, and Outerimpact. The screw comes with our red dot come with a pair of M3x6mm screws to connect to the pre-assembled picatinny mounting base. Some mounting plates made by other companies for specific handgun might need a longer screw such as M3x8mm or shorter screw such as M3x4mm depends on the thickness of the mounting plate/adapter. If you can’t get the screw to work properly, we recommend going to a local hardware store such as ACE Hardware to get the right size. 

We are an optic company that cannot provide all screws for handguns on the market because each handgun has different dimensions of the mounting plates, some are made to be optics ready, some need to replace the rear sight. We can name 3 different handguns, they all use three different screws. It is one of the main installation problems that our customer has. The handgun manufacture recommends users to contact the optics company, but we as an optics company do not know the specifications of the plate not made by us. We make the red dot to accept the industrial standard footprint. The pistol manufacturer (or machine shop) makes the plate for the same footprint, but they have their own options to decide which type screws that the plate needs.

I tried to call customer support but can’t reach a live person.

Answer: If we missed your call, please send e-mail to, to submit a message, you will get reply within 8 business hours guaranteed.