Interfit INT333 Strobies Boom Arm Extended arm VALVAB Description. The Strobies Boom Arm allows an assistant to hold your lighting above the subject. Each Arm has a padded grip & a cover at the base for a comfortable & strong grip. The arm has telescopic joints for extended use above the subject. ideal to be used with Strobies XS brackets Triple Flash Brackets Strobies Pop up Softboxes Strobies Radio sets with Strobies accessories attached such as a softbox or beauty dish.