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(Pocket-lint) - Acer has kicked off the Ultrabook flurry at CES 2012 by unveiling the Aspire S5, described as the "world's thinnest Ultrabook", and the Aspire Timeline Ultra.

The new Acer Aspire S5 is a slimline notebook, only 15mm at the thickest point, featuring a 13.3-inch display, going up against the MacBook Air. It packs in an Intel Core processor and SSD to ensure speedy performance, but otherwise the tech specs are still something of a mystery.

Acer is keen to stress the design of this new Ultrabook however, describing a "delicately curved" chassis with a mag-alu alloy palm rest and cover. We liked the look of the Aspire S3 (pictured above), if not the overall build, and hopefully this second-gen Ultrabook will move things forward a little. 

Adding another flourish of detail is what Acer are calling the MagicFlip I/O, which is essentially a cover for the ports (HMDI, USB 3.0, Thunderbolt). According to the details, you press the button and it flips down, ensuring a clean and sleek design when they are not in use. You'll also get Dolby Home Theater tuning, as we saw on the predecessor.

Acer has also announced the launch of the Aspire Timeline Ultra range. Coming in either 14- and 15-inch screen sizes, the new models will promise 8 hours of battery life, an Intel Core processor, dedicated graphics for intensive 3D gaming and even a slim DVD-Super Multi optical drive. 

Acer says you should think of it as a slimmer and lighter version of earlier generations of the Timeline series. The new range will measure just 20mm thick.

Other specs include an SSD/HDD storage option, Dolby Home Theater, HDMI and USB 3.0 ports, as well as the company's Instant On and Always Connect tech (common to both models) that lets users manage their multimedia and data on all their devices at anytime, anywhere - even from sleep.

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"The Ultrabook is much more than just a product segment. It's a new trend that will become the mainstream for mobile PCs, and customers will see the unique features gradually extended across Acer's notebook family", said Jim Wong, president of Acer Inc.

The Aspire S5 will start shipping in Q2 2012, the Aspire Timeline Ultra in Q1 2012, no word on pricing just yet.

Writing by Chris Hall.