... available with locking triggers as well. ROUND RING (3-ring metal): Standard Capacities: 1/2", 3/4", 1", 1-1/2", 2", 2 ... closing booster. When measuring ring metal capacity, measure area shown by arrow.ANGLE D RING (3-ring metal):Standard Capacities: 1", 1-1 ... not include any curved part of metal.STRAIGHT D RING (3-ring metal):Standard Capacities: 1/2", 3/4", 1", 1-1/2", 2 ...