I have a few Bowens mount softboxes, including a Phottix 105cm (41 inch), which is a go-to for a lot of my photography. This Bowens mount was a total failure. First, the softbox does not fit securely to the mount -- there is no familiar 'snap' and only a single tightening screw that is not tight enough. Second, the softbox was too heavy; the vertical stem could not support the weight and would pull the adjustable portion down.
A third issue I had is that I intended to use this mount for securing the StellaPro Reflex to my lightstand rather than purchase the separate lightstand mount accessory. But this mount is so designed that I couldn't mount a bounce umbrella with it.
Bottom line -- I returned the Bowens mount and because I don't want to purchase new softboxes, I returned the two Reflex lights that I had also purchased.