These caps are designed to go onto the hose end and suction end of the Harbor Freight Fuel Transfer Pump. These are designed to keep debris out of the hose and pump while it is being stored. The potential HF# for this pump is 63847, 64124, and 56646. The caps have a small tab with a hole that can have a rope or shock cord attached so that they don't get lost. I printed them with PETG and then attached using shock cord so that they have enough tension to not fall off when the pump is hanging from the wall.