Ade Nuwa PRO created an iron sight curve at the end of the body, and also added two white dots on the curve. For the rear of part of the red dot to become a back up iron sight. With the ultra short design, the red dot provides a distance/gap on some full size optics ready pistols, to give enough distance to be a Co-Witness back up sight, in addition to the LED dot and pistol equipped iron sight. For non-optics ready pistols that need to use an optic plate/adapter to replace the pistol manufacturer equipped rear sight, ADE NUWA's rear white dot will act as a pistol factory original rear sight for Co-Witness. Comes with the adjustment tool, user manual, lens cloth, red dot cover, CR1632 battery, screws. Parallax-free & Unlimited Eye Relief. Made of aircraft aluminum in anodized black finish with multi-coated lens. Comes with 3 pairs of screws for Sig P365XL/X, Springfield Hellcat OSP and Canik TP9 Elite SC ONLY. The provided screws might NOT work with EVERY compatible pistol listed. ADE makes the red dot to accept the industrial standard footprint. The pistol manufacturer makes the optic cut/slide for the same footprint, but they have their own opinions to decide which type screws that the screw holes take. ADE Does not know the screw spec every pistol manufacture used for their screw hole. Please ask the pistol manufacture what screw specs they used on the hole and ask them to provide the screw. If you cant get the screw to work properly, we recommend going to a local hardware store such as ACE Hardware to get the right size. Designed to fit Canik Elite TP9 SC, Canik METE SFX, Canik METE SFT, METE MC9, Sig P365X/P365XL/P365XL SPECTRE COMP, Ruger Max-9, Glock 43X MOS/48 MOS(not compatible with regular glock 43x/48 that are not MOS), Springfield Hellcat OSP, S&W Shield 2.0 Optics Ready, S&W MP9 EZ, S&W M&P shield plus performance center, Walther PPS M2 Optics Ready, Girsan MC1911SC Ultimate or any pistol/mounting plate/slide with RMS/RMSC screw pattern/footprint.