#HTE

Great Design: Butane Refill Canister Caps with Built-In Adapters

Some brands of butane refill canisters have five conspicuous circles on top of the cap:

Those are break-off adapter tips, so that you can refill different brands of lighters.

These have been around for decades, and sadly the original designer is unknown. But I think it’s an example of great design. They spent a little more money on the molds and perhaps pennies in extra plastic to make things easier for the end user.