If you have a Nokia phone using the muli-pin type plug for the headset e.g. N Series you may not wish to be saddled with the standard Nokia "earbud" headsets and would like to use some better quality headphones of your choice.
The solution is to purchase a 3.5mm adaptor kit, there are usually plenty on ebay but there are things to be aware of. There are a number of sellers which sell adaptors at very low prices e.g 99p. A lot of these are either poor copies or completly lookalike fake versions.
These copies all have the same thing in common and are usualy a) Mono and b) Have low volume output. Avoid cheap tubular shape adaptors, these are not made by Nokia and even some sellers have so called "genuine" adaptors for sale such as lookalike Nokia AD-49 sets, again these fakes are Mono and very low volume and are almost impossible to spot as the packaging and the set is identical to the real thing except minor differences in the label on the set itself. If you get one ask for a refund!
A genuine Nokia adaptor is a worthwhile investment as the stereo audio quality through good headphones is fantastic and the built in clip on mike in the set gives full handsfree capability. you will never want to go back to cheap earbuds again