I was seduced by the recent sale on Sigma ART lenses and ordered the Sigma 20mm f/1.4 DG HSM ART. Just unpacked it late last night, and was shocked by how big it is. Big. Really Big.
But it feels well made, and in very preliminary tests seems to focus beautifully on the Metabones (standing in until the Sigma adapter arrives.)
Makes the Batis 25mm seem tiny.
That lens 'hood' on the Sigma is not removable by the way; it's part of the lens and is needed to protect the huge, bulging, front element.