This adapter will convert your male 5.5mm barrel plug with a 2.1mm centre-pin to a male 5.5mm barrel plug with a 2.5mm centre pin.

Some of the new gadgets and devices requiring a higher current need a 2.5mm centre pin for a reliable connection, the TS100 soldering iron for example.

Most readily available "Wall-wart" power adapters have the more common 2.1mm centre-pin.