The Denali trim of the 2015 GMC Terrain includes all of the standard features found on the SLT-2 trim, plus Denali-specific wheels (18-inch wheels on four-cylinder versions and 19s if you get the V6), rear cross-traffic and side blind-zone alert systems, an eight-way power passenger seat, and special exterior/interior trim details. A navigation system is optional for all GMC Terrains, except the S Learn more