The Manfrotto Ezybox Pro Speedring Plate for Bowens allows you to attach the Ezybox Pro Square, Octa and Switch softboxes to Bowens (and other manufacturers using the S-Type fitting) studio flash heads.
The Manfrotto Ezybox Pro Speedring Plate - Bowens S-Type would be the best fit for studios and professional photographers looking for a compact, yet robust light box with a speed ring.
