ProMediaGear Spigot Stud Light Adapter for Profoto B2 Head on Flash Bracket, with 1/4"-20 Female Threads Mounts with a 1/4 inch-20 standard screw to the boomerang shoe The only piece needed to quickly mount B2 head onto Boomerang Flash Bracket Weighs: 0.07 pounds = 34 grams 1/4 inch-20 threads on both ends Anti Rotation, fits into channel grooves in Boomerang Shoe