bought it to use with the many Pentax K-mount lenses (of various generations) that I use on the Pentax KP, including the Sony A7r 2 that I recently added to my kit. The adapter is well made and is made of very solid metal for the structure, for the connector and for the bayonet. The polished metal notched ring seen in the center allows the membrane to be closed between the maximum and minimum of 11 positions without reference. Basically, you can close the aperture of any lens, but you don't know exactly what value it's set to (other than, of course, the two extremes that correspond to the maximum and minimum of the lens mounted). This obviously applies to the most modern optics without their own aperture ring. The rotation of this ring, which basically wants to simulate the membrane ring, is quite fluid and has small shots to facilitate positioning as much as possible. I've used it with various Pentax APS-C lenses, from the old 50M 1.4 to the Sigma 18-35 f/1.8 Art and 17-70 f/2.8-4 C. All work flawlessly, always within the limit , which is imposed on the most modern models of an approximate selection of the membrane. Obviously there are no electrical contacts, so there's no exif data on the optics and the focus is only manual (but the A7R2 is excellent in that regard). It is precisely the need to focus manually and without an electronic connection that prevents the use of some modern lenses, that is, those in which the focus ring does not work mechanically, but through the camera module. For example, the DA 18-50 WR RE, a very versatile and lightweight lens that I personally hold in high esteem, is sadly useless as there is no way to focus. Apart from this limit, which the adapter obviously cannot fix, the product is very valid and allows you to take excellent quality images of optics designed for another brand. In particular, the Sigma Art 18-35 still offers spectacular photos, even if you use the APS-C crop mode (however, with the 42Mpixels of the A7R2 sensor, you can take 18Mpixel photos, which are still valid).