7artisans 25mm/f1.8 features a seven-element, five-group design. It has a maximum relative aperture of F/1.8 to F/16 through its range. The minimum focal length is 0.18m with the length of 32mm and the diameter of 51mm. Ideal Aperture with Twelve Blades: Twelve diaphragm blades are crucial to favorable rendition of highlights in the fore and background. It provides high quality of the transition as well as nice bokeh for the lens, keeping the background intentionally blurred to keep the attention of the observer on the main subject.Portable Aluminum Mount: With aluminum-made body and copper bayonet, 7artisans 25mm / f1.8 weights as light as 143g, which is portable for your photography. Price is fixed. Do not trade. Interested can PM me @ 84298110. Thanks.