Lots of reviews on the Holosun so I will pass on doing that. What I want to review is the customer service - 5 - star. Great website to help you find what fits and then fast shipping. I wish all companies were this good.

Putting my new green dot on my S&W 5.7 made it exponentially more accurate and lethal! I was placing consistent 5inch body mass groupings right off the bat at 75 feet, very impressive.

Holosun 507K X2 Green Dot ACSS Vulcan Reticle - HE507K-GR-X2-ACSS

Very easy to stay on target, even during rapid fire. Clear visual acquisition at various distance. Highly recommend this, especially if you carry concealed.

I just cant say enough about Freedom Gorilla's service. Not only will they save you $$ but they are far more responsive than most similar online vendors. They also offer extensive online materials to assist in choosing the right optic product.
This new Holosun optic developed with Primary Arms offers a new approach useing a wide dotted circle to guide keeping the gree-Dot on target. It takes some practice but can make a real difference for rapid firing a pistol. There are other new options for Holosun pistol optics as well so I advise taking a good look before buying.