Amid rumors about a thinner iPhone, Tecno has unveiled a phone concept called the Spark Slim that's skinnier than a pencil. I got to hold it atthe Mobile World Congressin Barcelona, and it's certainly the lightest and thinnestphoneI've ever encountered (the company says it's just 146 grams).Slim phones are everywhere in 2025Typically, a narrower phone could mean compromising on things like battery life and camera, both of which phone buyers still rank among their highest priorities. But Tecno says the Spark Slim has a 5,200-mAh battery and two 50-megapixel cameras, one wide and one ultrawide.And if you're nervous about sitting on your phone and inadvertently turning it into a foldable, the company said not to worry, as the Spark Slim would use Corning's Gorilla Glass on the display and feature options for a ceramic or stainless steel backing. Tecno said that storage has yet to be determined since this is still just a concept.A thin phone that folds out into a 10-inch tabletThe company also showed off another concept called the Phantom Ultimate 2, a tri-fold phone that's 11 millimeters wide when folded and 3.5mm at its thinnest when unfolded. Its unfurled display measures 10 inches. Tecno says development on this device is so early that the company doesn't have any battery capacity or storage specs to share. The Phantom Ultimate 2 is another superthin phone concept from Tecno, this time in a foldable. Abrar Al-Heeti/CNETThin phones are certainly having a moment, with the reveal of Samsung's Galaxy S25 Edge in January and the release of Oppo's superslim foldable, the Find N5. Apple is also said to be developing an "iPhone 17 Slim" that could be released in the fall. Whether the Tecno Spark Slim joins the party of real-world devices remains to be seen, but perhaps those chances aren't as slim as they may once have been.