It's the first lens I bought to use with my K-5, and it's probably the lens I've used the most. It's Sigma's first take on the 17-70mm focal length, the zoom range that makes the first step up from a normal kit lens for so many of us:
Sigma 17-70mm F2.8-4.5 DC Macro Lens Reviews - Sigma Lenses - Pentax Lens Review Database

I've used this lens for candid photography, landscapes, product photography, sports, astrophotography, and even a low-key wedding. While its autofocus integration with my K-5 body gets confused sometimes, the overall performance and versatility of the lens has kept it in my camera bag for more than eight years!

The attached photo shows what the lens can do when everything is working together.

Thank you for your consideration.