Following through on a promise to add versatility to its product line, Palm on Monday is unveiling two slim new models that add a postage-size expansion slot. As previously reported, the $449 (£314.46) colour m505 features 8MB of memory, a Secure Digital expansion slot and a 16-bit colour screen. The $399 (£279.45) black-and-white m500 is slightly thinner than both the m505 and the Palm Vx and is roughly the same height and width as the Vx. Both units feature the new version 4.0 of the Palm operating system and a new lithium-polymer battery that offers much improved battery life. Both also come bundled with Palm's mobile Internet kit, which allows a handheld to use a nearby mobile phone as a wireless modem using either a cable or by beaming data through an infrared port. "This is the set of products that goes after the heart of Palm's market -- mobile business professionals," said John Cook, senior director of product marketing for Palm. "They get to keep the things they liked about the Palm V... but now they have options for expansion and for colour." Palm plans to make the m500 widely available and the m505 available in limited quantities by mid to late April. The m505 should be widely available in May, Palm said. Palm's new models come as other handheld makers also are updating their lines. Handspring last week introduced its Visor Edge, a slimmer model that offers expansion through a new connector or through and attachment that can use modules for the company's Springboard slot. As reported earlier, Hewlett-Packard plans to introduce a cheaper color version of its Jornada handheld. "This is a really great time to purchase a PDA," said Microsoft product manager Ed Suwanjindar. "Companies continue to raise the bar for what these devices can do." The two Palm models use a new type of connector that allows connection to a PC using either the included USB cradle or an optional serial cradle. While the new connector is not compatible with the Palm V series, Cook said Palm has promised developers that it will use this new connections on all new models for at least the next two years. Cook said that should make it more attractive for companies that want to make add-ons for the Palm. Kodak, for example, has already designed three different versions of its Palm Pix camera, including one designed to attach to the new Palms. Cook said the camera maker's message to Palm was, "We want to support you but we can't keep doing this." Cook added that a common connector also makes it more attractive for consumers that might want to buy a new handheld without having to replace all their peripherals. Both units use the same 160 pixel-by-pixel screen that has been on earlier models rather than the more dense screen that will be part of Sony's new Clie. The Sony unit, which will be launched first in Japan, has a 320-pixel by 320-pixel colour screen and is also the first Palm-based handheld that can play digital audio files. In a bit of a surprise move, Palm is bundling free a host of applications including a photo viewer, e-book reader, more powerful calculator and Documents to Go, a popular program for viewing and editing Microsoft Office documents on the Palm. Palm will also include software from America Online and AvantGo as well as a link to its own MyPalm portal. With the new products on the way, Palm is cutting the price of the Palm V to $349 (£244.42), enough of a drop that Cook said the product should still find buyers. Cook said Palm does not plan to stop manufacturing the Palm V any time soon, noting that many corporate customers will need time to approve the new models. Palm plans to make available at launch seven Secure Digital expansion cards, including a 16MB expansion card, a card to backup the information on the Palm, a package of game software, a dictionary and thesaurus module and three cards with software for international travel. Also, at least one third-party wireless modem should also be available by the time the new handhelds are widely available, Cook said. By the end of the year, Cook said there should also be add-on devices that plug in to the expansion slot, including one that allows a Bluetooth connection as well as possibly a digital camera and modem. Cook said he also expects higher density expansion cards with at least 128MB and possible 256MB to be available by year's end. Suwanjindar said that Palm's addition of Secure Digital expansion slots is a move that may find its way into the Pocket PC realm, noting that Casio's EM-500 already accepts the similarly sized Multimedia Cards. "We're always behind industry standards," he said. "SD seems to be gaining quite a bit of momentum," he said. Take me to the Mobile Technology Special Have your say instantly, and see what others have said. Click on the TalkBack button and go to the ZDNet News forum. Let the editors know what you think in the Mailroom. And read what others have said.