This sight fits directly on  FNX 45 Tactical using  FNX 45 Tactical provided "doctor mounting plate" which comes with the pistol purchase.  When you purchase a brand new  FNX 45 Tactical from the store, there are 2 mounting plates for optics that comes with the pistol in the manufacturer packaging. One plate is for trijicon rmr, another plate is for Doctor. This green dot fits the Doctor mounting plates If you are NOT sure if this red dot will fit your pistol, please Click HERE to send us a message of EXACT model of your pistol, we will let you know if you need a optic plate(it could an aftermarket plate to replace the rear sight, or pistol factory provided plate for Optic Ready pistol) and we will provide precise information of the plate you need. You will receive the reply within 8 hours Monday-Sunday.   We have made several improvements since it's initial release in 2014. We have made it more durable to withstand recoil and improved the ability to hold zero. Designed in Oregon. Waterproof/Shock/Fog Resistant. Lenses are precision ground and polished to exacting geometries to virtually eliminate parallax and to provide a very clear, crisp sight picture. This red dot comes with a picatinny mounting base. It is also compatible with varies handgun mounting plates that replace rear sight dovetail. It is also compatible to Optics Ready pistols such as Glock MOS, Springfield OSP, Fully windage and elevation adjustable and lockable; Unlimited Eye Relief. 5 MOA. 5 Illumination Settings. Powered by a lithium CR2032 battery(Included) Ade Advanced Optics model RD3-006, RD3-009, RD3-012, RD3-013, RD3-015 are designed to fit the slide/footprint of mounting plate made for Vortex Venom, Burris Fastfire, Meopta, Docter, Insight, Eotech MRDS, Sightmark Minishot. Therefore Ade red dots are compatible for varieties of handguns with appropriate plate that is made for any of those brands. Ade Advanced Optics model RD3-011 is designed to fit slide/footprint/ pattern of mounting plate made for of Trijicon RMR only. Therefore any mounting plate made for Trijicon RMR will fits RD3-011 This ADE RD3-009, alone with RD3-006,RD3-012,RD3-013 do NOT fit Springfield HELLCAT OSP, because springfield Hellcat OSP red dot footprint is based on Shield RMS. ADE sights has the footprint of Doctor/Vortex Venom type footprint. This RD3-009, and RD3-006, RD3-012 and RD3-013 fits directly to "Optics Ready" pistols such as Glock MOS, Springfield OSP(non-hellcat), Canik TP9 SFX(non elite sc), Walter PPQ Q5 Match, FNX 45 Tactical, IWI Masada handguns that come with mounting plates that marked for DOCTOR/VORTEX VENOM type red dot. All mentioned above pistols must to be OPTICS READY model that comes with MOUNTING PLATE marked for DOCTOR/VORTEX. If not, user has to purchase after market mounting plate(not included with this red dot sight purchase) to replace the rear sight. When you first receive the red dot. It has a picatinny mounting plate pre-assembled. Please use 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. Payments are accepted through Paypal.  We ship through USPS First Class Mail from Oregon, west part of the country should receive in 1-3 days,middle part and east part of the country should receive in 3-6 days!NO INTERNATIONAL SHIPPING! We promise our best quality and the lowest price for our customers, if the item is not as the description in the listing page, we will issue a exchange or full refund. if the item is the same as the description, we willl charge a 15% restocking fee. We are a new seller on Ebay, all our prices are really low compare to others, because we want to earn feedbacks. Please understand our feedback will be left once after we have received feedback from buyer. Our goal is to place a profit margin of $1 ~ $3 per item and sell in volume. As such, the more you save the more we make. While the others are selling 1 item, we are selling 10 ~ 20 items due to our price reduction.  Please use the "Ask Seller A Question" button. Please allow up to 24 hours for a response. Usually the buyer will get response in 6 hours.  Customer Satisfaction  • Please contact us right away (via eBay Messages) if you have any concerns, questions or issues about your purchase – and before you leave feedback.  • If you give us the chance, we will make every effort to make it right for you! • We strive for five stars from you in feedback – and work hard to earn it.  • Customer satisfaction is very important to us and our goal is to have every customer want to be a repeat customer.