Using this durable plastic YS Adapter Clip from Leoben, you can connect any lights with the diameter of 20mm . an optional light arm with a standard YS connector.
The clip features the signature YS type mounting bolt, which fits through the hole at the top of the lighting arm and can be screwed into place and unscrewed again via the knob on the side. The top of the clip fits around the body of the light itself and holds it securely in place.
here is the way of how to decide the diameter of the light holder