The quick release mount allows to put the Piko on a handlebar. Cause of its design, the light will sit right in front of the stem. The mount itself is only 7 mm wide and does not need much space on the bar.
The mount is cnc machined and even the screws and bolts were CNC machined out of V4 stainless steel.
25,4mm handlebars is mostly used on older bikes. If in doubt, measure your handlebar!