The ProMaster Small Universal Cap Leash attaches to your lens and then has TWO different mounting methods for the cap. Either use the sticky pad for caps without a dedicated leash hole or take the sticky off and attach to the mounting hole on your ProMaster or other premium cap.
The Small Universal Leash is specially designed for lenses with smaller barrels to ensure a snug fit. If your lens takes a 43mm filter or smaller, try the ProMaster Small Universal Cap Leash