The idea of a "universal" connector or adapter is probably a little "overly-enthusiastic" on the part of the manufacturer. The one pictured, for example, wouldn't fit my strobes.
When buying strobes, it's a good idea to make sure that there are adapters (speed rings) designed to fit the line of softboxes one has (or wants to buy). Most of the leading strobe manufactures provide adapters for the more popular brands of softboxes, however. With "off-brand" strobes one needs to be more cautious.