The Retro Mobile Handset is a classic style handset like your old telephones. 3.5mm plug fits into blackberry, Iphone 3 & 4, Nokia brand and HTC. Instead of a head set or ear buds, use this handset and rest it on your shoulder while talking or skyping. Or if you want to use your phone in style and look classy doing it! 2.5mm and 3.5mm adapter included.