See and Buy this product on Amazon.com store (affiliate):
It is a great telephoto lens option with relatively few shortcomings considering its reasonable price point. Its optical performance should represent a meaningful upgrade for those using entry-level 55-200mm or 55-250mm kit zooms, and the F4 aperture saves weight and expense compared to constant F2.8 aperture alternatives.
There’s a lot to like about Tamron’s most recent lens, from the build to the excellent magnification to the excellent price. [...] It is a sharp lens, but is clearly outclassed by the larger Tamron 70-200mm f/2.8 G2 lens. I found the autofocus a little slower than expected [...] and also found the autofocus a little more prone to hunting in some situations.