A mounting arm is disclosed on one or free end of which a piece of electronic or other equipment (11) is mounted and the other end of which is detachably fastened to the edge of a desk or table (10) or other supporting structure. An arm member (14) has three moving joints that permit the equipment (11) fastened thereto to be moved with multiple degrees of freedom for desired positioning of the equipment. One joint utilizes a friction washer assembly (16, 31, 31 min ) and a preloaded torsion spring (28) counterbalancing the weight of the equipment. The torsion spring (28) tension is adjustable to compensate for differing weight of equipment on the free end of the arm.; Another joint utilizes a friction ball joint arrangement (15) having double concentric friction ball surfaces in an assembly that permits multiple degrees of freedom of motion and is easily removed from the remainder of the arm without disassembling the ball joint (15).