GMC Shows More of its Detroit-Bound Sierra All Terrain HD Concept

We first reported on the new GMC Sierra All Terrain HD Concept in mid-December, but since then, General Motors has released a slew of new photos. The updated gallery includes the first photos of the design study's interior that has been spruced up with higher quality and more luxurious materials than the standard Sierra, upon which it is based. Set to debut at next week's North American