The Zire 31 is a Zire Hanheld from palmOne. The product was first released in April 2004 as a replacement for Zire 21. It runs Palm OS 5.2.8 and features a color 160×160 display, a SDIO slot and a standard 3.5mm stereo headphones jack. The ROM includes RealOne player giving the device some digital audio player capabilities. They can be extended with 3rd party software, such as TCPMP. The Zire 31 has a 5-way navigator pad, but still only 2 quickbuttons, as opposed to the standard 4 on the mid-range Zires 71/72. It has now been replaced by the Z22, which lacks the SD/MMC/SDIO Expansion and headphones jack.