Meet HeatGear® Sonic: UA's newest and greatest baselayer innovation. Under Armour started the "performance" revolution in sportswear with the original HeatGear®. This latest fabric takes comfort to the next level-lighter, with a sleek, softer feel that you can wear all day. Hugs tightly onto your body like a second skin, this ultra soft, smooth t-shirt provide an extremely comfortable lightweight feel during intense workout.