24-inch operator reinforcement bracket, zinc coated, 12 gauge steel. The longer ORBs like this one are for bigger doors or setups where the opener arm connects further from center. Zinc coating keeps rust at bay. Clevis pin and cotter ring come with it. If your current ORB is bent or the mounting holes are worn, get the same length as what's on there now. Don't guess the size, just measure the old one or check the door specs.