WAG Boarding Steps™ Model SLM-12 is shipped with 1″ and 1-1/2″ hook sets. These size hooks fit most fiberglass boats and some pontoon boats. If your boat swim ladder has horizontal cross-members (rungs or grab bars) with cross-sections larger than 1-1/2″ diameter, you will likely need the adjustable hook kit. The adjustable hooks fit cross-sections of up to 4″ on boat swim ladders up to 16″ wide. The durable, black plastic hooks are easy to install and adjust. All proprietary functionality of WAG Boarding Steps Model SLM-12 is maintained. Each kit includes four (4) hooks.